Arpeggio Generator

How Arpeggiators Work: From Chord Symbols to MIDI Patterns

An arpeggio is a chord whose notes are played one at a time in sequence rather than simultaneously. The word comes from the Italian arpeggiare, meaning "to play on a harp." When you hold a C major chord (C, E, G) and pluck the strings one after another, you are playing an arpeggio. The arpeggiator, first popularized by the Roland Jupiter-4 in 1978 and the Sequential Circuits Prophet-5 shortly after, automates this process. You feed it a chord, and it cycles through the notes at a rate and pattern you define. That simple concept shaped the sound of synth-pop, house, techno, trance, and countless film scores over the past four decades.

Parsing Chord Symbols into Notes

This tool uses the Tonal music theory library to parse chord symbols into their constituent notes. When you type "Cmaj7," Tonal identifies the root note (C), the chord quality (major seventh), and the interval structure (root, major third, perfect fifth, major seventh). It returns the note names C, E, G, and B, which the tool then maps to MIDI note numbers 60, 64, 67, and 71. This approach supports hundreds of chord types, from basic triads to extended jazz chords like C13#11 and altered dominants like G7b9#5.

Understanding the interval structure of chords is what makes arpeggiation musically useful. A major triad (root, major third, fifth) produces a bright, stable arpeggio. A minor seventh chord (root, minor third, fifth, minor seventh) produces something warmer and more introspective. A diminished seventh chord (root, minor third, diminished fifth, diminished seventh) creates tension and instability. The chord you choose determines the emotional character of the arpeggio, and the pattern type determines how that character unfolds over time. If you want to explore chord construction in more depth, the Chord Finder and Chord Progression Generator on this site cover the theory comprehensively.

Pattern Types and What They Sound Like

The five pattern types available in this tool correspond to the most common arpeggiator modes found on hardware synthesizers and DAW plugins:

• Up: Notes play from lowest to highest pitch, then repeat. This is the default arpeggiator behavior on most synths and produces a rising, energetic feel. New Order's "Blue Monday" uses an up-pattern arpeggio as its iconic bassline.
• Down: Notes play from highest to lowest. This creates a falling, resolving quality that works well for intros and breakdowns.
• Up-Down: Notes ascend, then descend without repeating the top or bottom note. This produces a continuous wave-like motion. The up-down pattern is the most widely used arpeggiator setting in trance and synth-wave.
• Random: Notes are shuffled each cycle. Random arpeggiation adds unpredictability and is useful for generative textures and ambient pads.
• As Played: Notes cycle in the order they appear in the chord voicing (root position), repeated across octaves. This preserves the voicing character rather than sorting by pitch.

Subdivision, BPM, and Timing

The subdivision control determines how frequently notes fire relative to the beat. At 120 BPM with 16th-note subdivision, each arpeggio note fires every 125 milliseconds. Switching to 8th notes doubles the spacing to 250 ms, giving a more relaxed feel. Eighth-note triplets fire every 167 ms, creating a galloping rhythm that sits between 8th and 16th notes. The MIDI Manufacturers Association standard defines these subdivisions as divisions of the quarter note, and every DAW interprets them the same way.

The Web Audio scheduling engine in this tool uses a lookahead scheduler, the standard technique for accurate browser-based audio timing. Instead of scheduling each note with setTimeout (which drifts), the scheduler looks 150 milliseconds ahead and schedules all upcoming notes directly on the AudioContext clock. This approach, documented by Chris Wilson in his seminal article on Web Audio scheduling, achieves sample-accurate timing that matches hardware sequencer precision.

Gate Length: Staccato vs. Legato

Gate length controls how long each note sustains relative to the subdivision interval. At 100%, notes run continuously into each other, producing a legato, overlapping texture. At 30%, notes are short and percussive, creating a staccato pluck. The difference is dramatic: a Cmaj7 arpeggio at 100% gate sounds like a flowing pad, while the same arpeggio at 25% gate sounds like a sequenced pluck or bell. Most synth-pop and trance arpeggios sit between 50% and 70% gate, leaving small gaps that let each note breathe. Techno basslines often use 40% to 50% gate for tight, punchy results.

Swing and Velocity Accents

Swing delays every other note by a percentage of the subdivision interval, creating a shuffled or triplet feel. At 0% swing, all notes are evenly spaced. At 50% swing, the pattern approaches a triplet feel. The swing control on this tool follows the same principle as the MPC swing found in classic hip-hop production, where values around 54% to 58% became the signature feel of producers like J Dilla and Pete Rock. The Drum MIDI Editor on this site uses the same swing implementation for rhythmic patterns.

Velocity accents add dynamic variation by boosting the velocity of every Nth note. Without accents, an arpeggio at uniform velocity sounds flat and mechanical. Accenting every 4th note (the downbeat of each bar in 16th-note subdivision) creates a natural pulse that locks the arpeggio to the groove. Accenting every 3rd note over a 16th-note pattern creates a polymetric feel that is a staple of minimal techno and IDM. The accent amount controls how much louder the accented notes are, measured as a percentage added to the base velocity.

Octave Range and Pattern Expansion

The octave range setting duplicates the base chord pattern across multiple octaves. At 2 octaves, a Cmaj7 arpeggio covers C4 through B5, giving you 8 notes per cycle instead of 4. At 3 octaves, the range extends to C4 through B6, producing 12 notes per cycle. Wider octave ranges create sweeping, cinematic arpeggios that fill the frequency spectrum. Narrower ranges are better for basslines and rhythmic parts. The Roland Jupiter-4 and Korg PolySix, two of the first synths with built-in arpeggiators, offered 1 to 3 octave range controls, and that standard has persisted across every arpeggiator since.

Exporting MIDI for Your DAW

The exported MIDI file is a Type 0 Standard MIDI File containing a single track with all arpeggio notes. The file includes tempo (from the BPM control), time signature (4/4), and per-note velocity and duration data. When you drag the .mid file into Ableton Live, FL Studio, Logic Pro, or any other DAW, the notes appear on a MIDI track ready for any virtual instrument. Assign the track to a synth pluck, a piano, or a bell patch, and the arpeggio plays back exactly as you heard it in the browser. The MIDI to Sheet Music tool can display the exported file as notation if you want to see the pattern written out.

For producers building complete arrangements, a practical workflow is to generate 3 or 4 arpeggio variations from different chords in your progression, export each as a separate MIDI file, and arrange them across your song timeline. Combine this with the Chord Progression Generator to find the underlying harmony, and the Tempo Map Calculator to plan your song structure. These tools together cover the harmonic and rhythmic planning phase before you open your DAW.

Arpeggios in Context: Genre Applications

Different genres use arpeggios in characteristic ways. In synth-pop, arpeggios typically run at 16th notes with medium gate length and up or up-down patterns, providing harmonic motion under a vocal melody. In trance, arpeggios are fast (16th notes at 138 to 145 BPM), use up-down patterns across 2 to 3 octaves, and are heavily processed with delay and reverb. In techno, arpeggios are often minimal, using single-note or two-note patterns with short gate lengths and heavy velocity accents to create groove. In ambient music, arpeggios are slow (8th or quarter notes), use long gate lengths approaching 100%, and rely on random patterns for organic, evolving textures.

The arpeggiator's role in electronic music history is documented in academic research. A thesis by Mark V. Campbell at York University traces the arpeggiator from its origins in 1970s hardware synths through its role in defining the aesthetics of electro, house, and techno. Campbell argues that the arpeggiator embodies the defining characteristics of electronic dance music: synthetic, repetitive, programmable, and automated. Understanding this history helps you use arpeggios intentionally rather than as background filler.