An arpeggiator (often shortened to "ARP") is a feature on a synthesizer or music app that automatically plays the notes of a held chord one at a time, in sequence, instead of all together. Hold down a chord, and the arpeggiator turns it into a repeating melodic pattern on its own, without you having to play each note individually.
Where the Term Comes From
"Arpeggio" refers to the notes of a chord played in sequence rather than simultaneously, a technique musicians have used on acoustic instruments for centuries. An arpeggiator automates that technique, so a single held chord produces a moving pattern without manual note-by-note playing.
How an Arpeggiator Works
You hold down a chord (or sometimes just a single note, depending on the mode), and the arpeggiator:
- Reads the notes being held
- Plays them back in a defined order — up, down, up-down, or a more specific pattern
- Repeats at a set rate — synced to the tempo, often adjustable from slow quarter notes to fast sixteenth-note triplets
- Continues until the chord is released (or, in some apps, latches and keeps playing after release)
Common Arpeggiator Settings
- Rate: how fast the notes cycle, usually expressed as a note value (quarter, eighth, sixteenth, and so on)
- Pattern or direction: the order notes play in, such as up, down, or alternating
- Octave range: whether the pattern stays within the held notes or extends up or down additional octaves
- Latch or hold: whether the pattern continues after you release the chord, or stops immediately
Curated Phrase Patterns
Some apps go beyond a simple up/down arpeggiator and include curated phrase patterns: pre-built melodic sequences (not just a straightforward run through a chord's notes) that transpose to whatever root note you play. This gives more musical variety than a basic arpeggiator direction while still requiring only a single held note or chord to trigger.
Why Producers Use Arpeggiators
- Turning a simple held chord into a moving, rhythmic melodic part with no extra playing required
- Generating ideas quickly, since a pattern with an interesting rate and direction can suggest a whole track's rhythmic feel
- Adding movement to sustained pads or drones without needing precise manual timing
- Locking a melodic part to a scale automatically, especially useful for anyone without deep keyboard experience
Arpeggiator vs Sequencer
An arpeggiator generates its pattern live from whatever note or chord you're currently holding. A step sequencer, by contrast, is programmed in advance: you place specific notes at specific steps ahead of time, and the sequencer just plays back exactly what was programmed, whether or not anything is currently being held.
ARC-24 includes a built-in arpeggiator with a curated set of phrase-style patterns spanning classic, electronic, and ambient styles, each transposing to whatever note or chord you play, alongside six synth tracks, a drum machine, a sampler, and a drone layer. Learn more at arc24.app.
FAQ
Do I need to know music theory to use an arpeggiator?
No. An arpeggiator generates its pattern from whatever note or chord you hold, and many apps lock that note to a scale automatically, so you don't need to know chord theory to get a musical result.
What's the difference between an arpeggiator and a regular synth pattern?
An arpeggiator responds live to what you're currently holding, generating its pattern in real time. A pre-programmed pattern (in a step sequencer, for instance) plays back fixed notes regardless of what you're holding at that moment.
Can an arpeggiator be used with a drone or sustained pad sound?
Yes. Layering an arpeggiated pattern over a sustained drone is a common way to add rhythmic movement to an otherwise static, held sound.
Does an arpeggiator work with just one note, or does it need a full chord?
It depends on the app and mode. Some arpeggiators need multiple held notes to have anything to sequence through; others support single-note patterns that step through a phrase or scale pattern from just one held note.