Each transit line supplies an ordered set of stops. Leið maps those stops to musical pitches and plays them along the lane’s loop. The moving playhead shows where you are; a highlighted stop marks a note event.

The Map shows the routes in geographic space. DAW shows their musical structure. A route’s length and stop pattern provide the raw material; the lane controls let you compose with it.

Map/DAW is the main instrument: choose lanes, edit their notes, shape their sounds and mix them. Drum Machine is a step sequencer. Song arranges saved presets into a sequence of sections.

Switching tabs keeps visited tabs’ settings in memory. Playback pauses when you leave an area so separate engines do not play over each other. Return to a tab and press Play when you want to hear it again.

Choose between Budapest, Helsinki, Berlin, Prague, New York, Zürich and Warsaw from the app menu. Changing city changes the available transit lines. Save anything you want to keep before switching.

All seven cities currently use Mock mode: simulated vehicles and timing based on real route data. Live is disabled. The guide’s references to stops and vehicles do not mean that the current playback follows real-time arrivals.

Open the header menu for city selection, account controls, My presets, Plan & billing, Take the tour, Sound problems?, feedback and legal information. Theme controls are available on desktop.

Take the tour replays the introduction. On desktop it walks through lane controls and opens the device rack to explain the instrument, voice, pitch, filter, EQ, expression, timing, arpeggiator, granular, sidechain and sends. Sound problems? opens the sound check once the Map instrument is ready. The user guide opens separately so you can keep your current mix available.

Use Play to start and Stop to halt playback. BPM sets the shared musical tempo. Begin with a moderate tempo and one enabled lane so each change is easy to hear.

A browser requires a user gesture before audio can run. If the page is silent after loading, click Play yourself. If it is still silent, check lane power, solo selection and the master level.

Speed changes how quickly a lane moves through its stop sequence. Different speeds and loop lengths create phrases that drift apart and meet again.

Use the loop handles on the stop rail to choose the section that repeats. Stops outside the selected region are dimmed. A short loop makes a repeated motif; a longer loop gives the route more time to unfold.

Note length sets how long ordinary stop notes are held; legato, arpeggiator and PluckSynth use their own articulation, and Resonator/Macro behaviour varies by model. Short lengths make separated phrases; longer lengths overlap more readily. An instrument’s envelope also affects what you hear.

Glide slides between pitches. Legato connects notes rather than retriggering every note as a separate articulation. Their effect depends on the selected instrument; try a mono voice when exploring smooth bass or lead lines.

On a Poly / Pad lane, HOLD defaults to Fixed, which uses the lane’s LENGTH. Choose Demand to vary each stop’s hold between Shortest and Longest. The default bounds are a quarter note and one bar. Busier stops hold longer; use INV to reverse this so quieter stops hold longer.

On phone, open Rhythm and set Hold from to Demand, then choose Shortest, Longest and Invert. This uses the same estimated service demand as the Demand pitch contour, but you can use either feature independently. If a stop has no demand value, its note uses the fixed LENGTH.

Arpeggiator and legato use their own timing. Changing away from Poly / Pad keeps the demand settings stored but inactive. A new note of the same pitch can shorten the previous hold. Rail bars and the stop editor help you see the resulting length; the phone Notes list shows the requested hold.

Open the line picker to add a route from the active city. Lines already in the mix are shown as unavailable for addition.

Use a lane’s change-line action to replace its transit route while retaining its sound settings. The change picker also offers Remove this lane. Fresh route selections start disabled; enable the lanes you want to hear.

A disabled lane does not trigger notes and is excluded from the map and exports. This is useful for keeping an arrangement idea without hearing it.

Click Solo to hear that lane alone. Cmd-click on Mac or Ctrl-click on Windows/Linux adds or removes a lane from the solo selection. Clear solo selections to return to the enabled mix.

Duplicate opens a dialog asking for a chromatic pitch offset, up to 24 semitones in either direction. Choose 0 for a unison copy or another interval to build a harmony.

The copy inherits the source’s sound settings and can then be edited independently. Duplicates are musical lanes and do not add another route to the map. Chromatic duplicate transposition uses semitones; the stop editor uses scale degrees.

Give lanes role labels such as Bass, Lead or Pad and choose a tag colour to make a busy arrangement easier to read. These annotations help you navigate; they do not change the sound.

Use lane ordering controls to keep related musical roles together. The transit line name identifies the source even when you add a role label.

Root and scale define the musical pitch set. Octave moves a lane into a lower or higher register. Start related lanes in the same key, then separate bass and melody by octave.

Choose a Contour: Demand, Geometry, Geo, Walk or Arch. Variation, Pitch range and Maximum leap further shape the melody. The Harmony controls apply a shared key across lanes. Scales include Major, Minor, Pent., Pent. Min, Dorian, Phrygian, Lydian and Mixolydian. Pitch contour determines how stop information becomes a melodic shape. Demand uses a normalized estimate derived from scheduled service, route connections and network structure. It is a musical input, not a live passenger counter.

Click a note dot on the stop rail to open its stop editor. Raise or lower the pitch in diatonic scale degrees and set velocity between 20% and 100%. Changes apply immediately; there is no Apply step.

Velocity changes how strongly that stop is played. Stop chance sets that note’s probability independently of the lane. On phone, use the lane’s Notes list to reach stop settings. Per-stop changes work on original and duplicated lanes.

Lane note chance is the probability of playing each note. Stop chance overrides that probability for an individual stop. At 100% a note always plays; at 0% it is skipped. Intermediate values roll again on every pass.

A loop pattern makes a lane play a chosen number of its own loops and rest for a chosen number. Offset shifts its position in that cycle. Since each lane counts its own loops, unequal loop lengths produce longer evolving patterns.

Skipped notes do not trigger map flashes or sidechain events. A chance-based performance changes between passes, so an exported MIDI loop cannot predict every future random performance.

The arpeggiator turns a triggered note into a rhythmic pitch pattern. Enable it on a lane and use its style (Up, Dn, Up/Dn, Dn/Up, Conv, Div or Random), subdivision, gate, octaves, steps and distance controls to turn a sparse route into a busier phrase.

Balance arpeggiation against lane speed and note length. Use the per-stop velocity editor for accents rather than making every lane louder.

The lane instrument picker offers Synth, MonoSynth, DuoSynth, FMSynth, AMSynth, Poly / Pad (PolySynth), PluckSynth, MembraneSynth, MetalSynth, NoiseSynth, Sampler, Drums and Resonator. Macro appears when enabled for the deployment.

Use a mono voice for bass and glide, PolySynth for overlapping notes, FM or AM for bright complex tones, PluckSynth for plucked attacks, MembraneSynth for pitched percussion and NoiseSynth for noise-based rhythm. Available parameters follow the chosen voice.

Poly / Pad plays overlapping notes and offers Basic, FM and AM in its Voice selector. Basic gives a straightforward synth tone; FM and AM provide different modulation-based colours and their own sound controls. On desktop, find Voice in the POLY section; on phone, open Tone.

Change the voice to explore another timbre without replacing the lane’s notes. Voice-specific automation remains stored while that voice is inactive and resumes when you switch back. Pair these voices with the Demand hold option for changing pad lengths.

Attack is the time taken to rise into a note. Decay moves from the attack peak to the sustain level. Sustain sets the held level, and Release determines the tail after the note ends.

For a pad, try slower attack and release. For a short pluck, use a fast attack and shorter decay or release. Change one control at a time and listen at a steady volume.

Choose Sampler for recorded instrument sounds, including piano, Casio, bass, strings, winds, brass, guitars, organ, harp and xylophone. Pro members can also load a custom sample up to 50 MB and 60 seconds long, then choose its base note so it plays at the intended pitch. Custom audio is decoded locally in your browser and is not stored in the preset; load it again after a refresh or in a new session. The Pro upload control opens the upgrade view on Free. Check Licences & credits before reusing sample material, especially Casio sounds. Allow samples to finish loading before judging the sound or exporting. The route still supplies notes; the sampler provides their timbre.

A sample-based instrument may respond differently across registers. If a phrase sounds unnatural, try another octave, a different sample sound or shorter note lengths.

Resonator offers Modal, Sympathetic and String models with Structure, Brightness, Damping and Position, plus envelope and Bow controls. Higher Damping rings longer in this instrument. It uses an excited resonant model for ringing, string-like and other physical tones. Its dedicated controls shape the excitation and the way energy resonates or decays.

Keep long resonant tails in mind when setting note density, release and effects. Dense routes with long decays can build up quickly; lower the lane level before increasing resonance.

Macro is a multi-model synthesis instrument. Choose its model, then use Harmonics, Timbre and Morph to explore its sound. It is only offered in the picker and new AI plans when the deployment enables it.

Macro’s Envelope switch is Off by default. Turn it On for per-voice Attack, Decay, Sustain and Release controls: each voice holds for the note length, then releases. Physical and percussion models can still decay internally. Colour is inactive while the envelope is On. Choose 1 to 4 voices for overlapping notes; more voices use more processing. Glide and legato do not apply to Macro.

A saved song that already uses Macro can still play it even when the picker does not offer it. If you do not see the option, you do not need to change any account setting.

Lane volume sets its contribution to the mix. Pan places it left or right. The master level controls the overall output. Turn a competing lane down before raising another.

Use the meters as feedback and listen for clipping or excessive loudness. Output protection helps control peaks, but a balanced arrangement still starts with sensible lane levels.

A filter removes parts of a sound’s spectrum. Cutoff sets the boundary, and resonance emphasizes the area around it. Choose the available filter type or model for the musical result you want.

The Analog model provides a ladder-style filter character. Standard uses Q; Analog has Res, Drive and Slope. Bypass lets you compare. Move cutoff slowly while listening, especially at high resonance. A darker bass or pad can leave space for a brighter lead.

Use the lane EQ to rebalance frequencies within an instrument. Cut unnecessary low energy from supporting parts and reduce crowded midrange before adding more effects.

The master chain runs EQ, Glue, Warmth and Limiter in order. Controls include Low cut, Low-mid, Air, Warmth, Thresh, Ratio, Drive and Ceiling. Master volume is separate. Master processing shapes the combined result. Make small moves and compare at similar loudness. A louder setting can seem better even when it reduces clarity.

Sidechain uses note activity from another source to duck a lane. Choose another lane, all drums or a specific drum pad as source, then adjust duck depth, attack and release for gentle space or a rhythmic pumping effect.

If the source is disabled, resting or skipping notes through chance, it does not produce those trigger events. Check the source’s activity if the ducking disappears.

An FX send routes part of a lane’s signal to a shared effect bus. Raise the send on the desired lane, then adjust the bus controls and return level. A lane with no send to that bus will not gain that effect.

Send effects let several lanes share one reverb or delay. Keep dry lane levels and wet returns balanced so the route notes remain clear.

Space and repeats: Reverb, Spring Reverb, Delay and Ping-Pong. Movement: Chorus, Phaser, Tremolo, Vibrato, Auto Filter, Auto Panner and Auto Wah. Colour and width: Distortion, Bit Crusher and Stereo Widener.

Delay timing follows the units shown by the control. Feedback increases the repeats and can build energy; raise it gradually. Reverb impulse-response choices define the available spaces. Pro members can load a custom WAV impulse response up to 20 MB and 12 seconds long, with 1, 2 or 4 channels. It is decoded locally in the browser and must be reloaded after a refresh. On Free, the Pro upload control opens the upgrade view. Bus controls also provide wet level, mute, solo and removal.

The granular section depends on the deployment. The original granular layer and the Texture insert are different engines, so the controls you see can differ from another installation.

Texture Classic provides Position, Size, Pitch, Density, Texture, In gain, Dry/wet, Spread, Feedback, Reverb and Freeze. Mk II uses Time, Size, Shape and Pitch with randomization, plus Density, Feedback, Dry/wet, Reverb, In gain and Freeze. It offers Hi-fi, Clean tape, Vintage and Dirty tape quality, and Gates, Clock or Free seed modes. With Texture, Classic and optionally Mk II provide granular processing. Mk II Size at the far left reverses grains; fully right acts as a delay. A song already using Mk II can play it even when the model picker does not offer it. This is deployment availability rather than a missing upgrade.

Grain size controls the length of small audio fragments; density and timing affect how those fragments overlap. Pitch, position and spread can turn an ordinary phrase into a cloud or texture. Use only the controls available in your selected model.

Freeze holds material for sustained processing. Blend dry and wet to keep the original note attack or move into a fully processed texture. If a freeze contains silence, let audio enter the processor before freezing again.

An automation lane uses a transit route as a modulation source for a chosen parameter. Select a source, destination and available range or shaping settings, then play to hear the movement. Destinations include FX sends, Volume, Pan, Glide, filter controls, ADSR and supported instrument or Texture controls. An automated control can be unavailable for manual editing.

Active musical lanes are excluded as automation sources so picking a source does not silently remove an audible instrument. Choose an available inactive line when creating modulation.

Begin with a narrow range on an easy-to-hear destination such as filter cutoff or an effect amount. Then widen it or choose a slower-moving source as the arrangement needs.

If a parameter seems to move by itself, inspect automation before correcting its manual setting. Removing or replacing a route can also change which modulation and sidechain sources are available.

Drum Machine has Kick, Snare, Hat, Rim, Ride and Clap rows, driven by selected transit routes. Click a step repeatedly to cycle full, normal, soft and off. The sequencer holds 64 slots and shows a sliding 16-step window. Use offset to explore other parts of the pattern.

Select routes and regenerate to make a new starting pattern. Mute a row, clear a row or clear everything to build by hand. Use BPM and Play/Stop to audition, and MIDI to export the drum notes.

Send to Map brings the drum pattern into the main arrangement. The resulting drum lane can be balanced with the transit instruments.

The sent pattern is linked in both directions: later changes in Drum Machine and the Map drum lane synchronize. Save your Map preset after the final edits so Song Chainer uses that version.

Choose Drums as a lane instrument to use its drum editor in the arrangement. Drum controls and note behaviour differ from melodic transit lanes.

Drums are excluded from the Free plan’s active transit lane count. Use lane power, mix controls and effects to place the pattern under the route-based parts.

Open the app menu to create an account or sign in with email and password or a magic link. Cloud saving requires a signed-in session.

The song menu provides New, Open, Save, Save As, Rename and Autosave. Use it to name and save the current setup. Autosave is session-gated; check the save status before closing or switching away. Save As makes a separate preset for a variation.

Use the song menu or My presets in the app menu to return to saved work. My presets also provides sharing and deletion controls.

Opening from My presets reloads the app into Map with the selected preset. Save current work first. Deleting a preset is a lasting account action; check whether a composition uses it before deleting.

Enable sharing on a saved preset and copy its public link. Anyone with the link can open the shared song; treat its contents as public.

A visitor can use Save As to keep their own copy when signed in. Turn sharing off to revoke the original public link. Existing copies are independent presets.

A preset stores the city and lane setup together with sound settings, note edits, mix, effects, automation and arrangement-related lane state. This lets the same route become several different pieces.

New, reset and city-switch actions can replace the current setup. Save variations deliberately instead of relying on a browser tab staying open forever.

Use a lane’s MIDI export for one part. The header MIDI control downloads a separate .mid file for each audible lane, in sequence. If your browser asks, allow multiple downloads. Import the files into another DAW and assign instruments there.

Each file contains exactly one pass of that lane’s selected loop, starting at time zero. It follows loop region, speed, grid, pitch edits, note length and arpeggiator steps. Notes are clipped at the loop end and shortened before the next note of the same pitch. MIDI export does not record the whole playback session.

MIDI carries notes and timing rather than the sound of Leið’s synths and effects. Disabled lanes and lanes excluded by solo are omitted. One-loop export omits stops with 0% chance; intermediate probabilities do not predict all future performances.

Export a lane stem or the full mix as WAV to capture actual audio. Audio capture runs in real time during a playback pass, so allow it to finish and keep the tab in the foreground.

Finish loading samples and choose your mix before recording. The capture window is based on the musical loop lengths. For evolving chance patterns, each capture can be a different performance.

Choose MIDI when you want to rearrange notes or use other instruments. Choose WAV when you want the rendered sound for listening, video or further mixing.

Export access is metered on Free. Check Plan & billing for remaining usage before starting several exports. Export controls are in Map/DAW and Drum Machine; Song does not provide a separate composition export.

Save your Map presets first, then open Song. Add presets as parts in the order you want them to play. Choose how many bars each part lasts, from 1 to 64.

Song uses the saved versions of presets. Unsaved changes in Map are not automatically the version used by the chain; return to Map and save if you want those edits included.

Choose Cut for a direct change between parts or Crossfade to overlap them. Crossfade length can be set from 1 to 16 bars.

Use cuts for deliberate section changes and crossfades for gradual shifts of texture. Listen through the boundary: overlapping dense presets can make a transition much louder.

The loop strip shows how a preset’s lane cycles relate. Realign and snap hints help you choose section lengths where loops meet; play/rest cycles are included in that relationship.

Use the row’s Play from here action to audition a later part without starting from the beginning. Reorder, adjust or remove parts, then listen across the transitions.

Use New, Save, Save As, Open and Delete to manage compositions separately from individual presets. A composition keeps preset references, durations and transitions. Keep its referenced presets available.

Set the chain’s shared BPM and Loop option for playback. Check any city mismatch warning before playing. Free compositions can contain up to three parts. Song has no separate export control.

Open AI Composer. Choose New idea to start a fresh setup or Edit current to change an existing one. Edit current needs an enabled lane. Choose Auto or a genre recipe and describe the result you want.

For example: “A slow, sparse piece with a low bass, soft plucked melody and a little delay. Leave room between notes.” Select Generate or press Cmd+Enter / Ctrl+Enter.

Review the returned plan and any advisories. Apply & Play commits the proposal and starts playback. Discard leaves the proposal unapplied.

New idea resets reused lanes to a clean sound baseline. Edit current preserves settings the plan does not specify. Be specific about which lane or musical role you want changed. Generation needs the service to be configured and available.

When enabled for the deployment, Connect an AI client appears in the app menu. A Pro account is required to connect; Free accounts see an upgrade view. The in-app AI Composer is a separate workflow.

Under Add the server, copy the remote MCP server address shown there (your site’s /mcp endpoint) into a compatible client, then sign in and authorize access. The linked MCP setup guide provides client-specific instructions. Review the requested access before authorizing.

Install the composer skill is an optional second step. Use the linked installation guide or download the Composer skill ZIP; in Claude, add it under Settings > Capabilities > Skills. The skill helps a compatible client follow Leið’s composition workflow.

Manage authorized clients in Connected clients and use Disconnect to revoke access. Saved-song edits made by a client appear after reopening the song in Leið. If the menu entry is absent, MCP is disabled for that deployment.

Phones load the music-making app with touch-oriented controls. Tap a lane to open its Tone, Rhythm, Mix and Notes sections. Full envelope, filter, EQ and granular editors are desktop-only; use desktop for detailed sound design.

Use the Notes list to edit individual stops. The More/session sheet provides Harmony, Re-pick all lines, Add or Update drums, AI Composer, MIDI/WAV and Sound problems?. Close the sheet to return to the arrangement.

Use the phone’s app navigation to switch Map, Drum Machine and Song. City selection lives in the menu. Theme switching is hidden on phones.

Keep the page in the foreground for playback and recording. Mobile browsers may pause audio when the phone locks or the browser is backgrounded. Start with a few enabled lanes if a dense arrangement struggles.

Free includes up to 6 active transit lanes, 3 parts per composition, 3 exports total and 3 AI generations total. Drum lanes do not count toward the active transit lane allowance.

Pro removes the lane, composition-part and export limits, enables custom sampler and impulse-response uploads, and includes 50 AI generations per UTC calendar month. Connecting an external AI client also requires Pro when MCP is enabled for the deployment. Plan & billing shows your actual access and usage. No subscription price is fixed in this guide.

If a preset exceeds your lane allowance, its settings are retained while excess lanes are disabled. Disable another lane to make room or use a plan that supports the larger mix.

A missing instrument model or granular engine option can also be a deployment setting, separate from your subscription. Check the relevant chapter before assuming a preset is broken.

Use Profile for account information, Change password for password updates, and Plan & billing for subscription and usage information. Use the billing controls provided there to manage a subscription.

Feedback and the legal documents are available in the app menu. Include your browser, device and reproduction steps when reporting a problem; avoid including passwords or private account details.

Click Play, enable at least one lane, clear unwanted solo selections, and check lane and master levels. Check your device output, headphones and browser tab mute setting.

Wait for sample or instrument loading. Open Sound problems? from the app menu for the built-in sound check. On mobile, bring the page into the foreground and try Play again.

Lower the master and lane levels. Reduce enabled lanes, dense arpeggios, long releases, granular density or costly effects. Try a simpler arrangement and add processing back gradually.

High resonance, delay feedback and overlapping crossfades can increase energy. If a problem persists, stop playback, save if possible, reload, and report the exact steps that reproduce it.

For cloud saves, confirm you are signed in and online. For metered actions, check Plan & billing. AI also needs its server service to be configured; a service failure is different from an invalid musical prompt.

If a feature is described as optional in this guide, it may be disabled in the current deployment. Live mode is currently unavailable in every city.

Leið automatically retries a failed tab download. If the tab still shows a loading error, check your connection. Save any current Map work before using the error’s Reload button, then open the tab again.

Cmd/Ctrl-click Solo: add or remove a lane from the solo set. Cmd/Ctrl+Enter in AI Composer: generate a plan. Cmd/Ctrl+S: save. Cmd/Ctrl+Shift+S: Save As. Escape: close the top open dialog. Tab and Shift+Tab: move between controls.

Click a stop dot: edit its pitch and velocity. Drag loop handles: select the repeating region. On phone, open the lane sheet and Notes list instead of trying to use tiny rail controls.