Online Arpeggiator & MIDI Export.

How to make an arpeggio and MIDI file

1. Choose the harmony. Choose a root and chord quality, then optionally add up to eight chord slots for a progression.
2. Set the motion. Select a pattern, octave range, note rate, tempo, length, gate, swing, velocity, accents and inversion.
3. Regenerate and edit. Regenerate the steps, then enable notes or edit pitch, velocity and duration directly in the step table.
4. Preview and export. Use Play for the local reference synth and Stop or Escape to cancel even a preparing audition. Export the current event model as MIDI or JSON, or its rendered audio as exact-frame WAV or locally encoded MP3.

Keep audition and export under your control

Preparing is not playing. Play may first render the current steps and wait for browser audio. Stop remains available during that wait; Escape also cancels an unfinished render or pending audio download. A stopped audition never starts later when the wait ends, and returning to the page requires a fresh Play.

Stop and Cancel render are different. Stop retires the audition but can leave a useful render finishing locally. Cancel render discards partial PCM while keeping your editable chord-tone steps. After a playback error, press Play to retry; if the browser blocks audio, allow playback first.

Download the model you reviewed. Changing a setting, regenerating or editing a step retires an unfinished old audio export. WAV uses the current 48 kHz stereo reference-synth buffer; MP3 encodes that same buffer and may add codec padding. MIDI has events rather than the preview instrument's sound; use JSON to retain the musical settings and event receipt.

A focused arpeggio sequencer, not a general composer

This arpeggiator sequences the notes already defined by your chord choices. Up, Down, Up-Down and Down-Up are deterministic. Played preserves the resolved chord-tone order, while Random uses a visible seed that can be reproduced or mutated. Gate is a percentage of the selected rate. Swing delays every second step by the selected percentage of one step while the grid length stays fixed.

It is deliberately different from the Chord Progression Generator, which creates and sounds block chords; a melody generator, which follows a scale and contour; and a bassline generator, which builds a low-register groove. This page only turns chosen chord tones into an arpeggio.

Patterns, octaves and timing

Directional patterns

Up and Down visit every expanded chord tone once. Up-Down and Down-Up reverse through the inner notes so neither turning endpoint is duplicated.

Rate and triplets

The 480 PPQ grid uses 480 ticks for 1/4, 240 for 1/8, 160 for 1/8T, 120 for 1/16 and 80 for 1/16T.

Gate and swing

Gate multiplies the nominal step ticks. Swing delays odd-numbered steps by rate ticks × swing percent without moving the following grid line.

Accents

Base velocity applies to every step; an optional interval adds a bounded boost to every nth step.

MIDI, WAV, MP3 and JSON parity

One bounded event list drives the piano roll, synth and every download. MIDI is a format 0 Standard MIDI File with one 480 PPQ track, explicit tempo, matched note events and an end marker at the musical grid duration. WAV is rendered at 48 kHz to the exact calculated frame count. MP3 is a lossy local encoding of that same exact source buffer and may report codec padding in some players. JSON records settings, chord spelling, steps, ticks and exact source-frame duration.

Safety bounds: up to eight chord slots, four octaves, 32 bars or 16 cycles, 4,096 generated steps and 180 seconds of 48 kHz stereo PCM. Changing a musical setting marks the current steps and audio stale; regenerating creates a fresh bounded model. Cancelling discards partial audio.

FAQ