What Is an Arpeggiator?

An arpeggiator takes the notes of a chord you are holding and plays them one at a time in a repeating pattern, at a rate you set. Hold three notes and you get a three-note loop. Hold four and the loop is four long. By the end of this page you will know what each control does, how to set one up with specific settings, and how to tell an arp from a sequencer by ear.

What does an arpeggiator do?

An arpeggiator turns a held chord into a stream of single notes. You hold the notes, it chooses the order and the timing. Let go and it stops.

The name comes from arpeggio, the term for a chord played one note after another instead of all at once. A pianist rolls a chord by hand. An arpeggiator does it for you, in perfect time, for as long as you hold the keys, and faster than any hand can manage. Sound On Sound’s Paul Ward put it plainly in 1996: “Arpeggiation is basically the playing of chord patterns by sounding each note in a sequence, rather than simultaneously.”

What makes it an instrument rather than a trick is that it is live. Change the chord and the pattern changes with it, on the next step, in time. Nothing was programmed in advance.

The controls: direction, rate, octave range, latch, gate

Almost every arpeggiator has the same five controls, under slightly different names. Direction sets the note order, rate sets the speed, octave range sets how far the pattern climbs, latch keeps it running after you let go, and gate sets how long each note sounds.

Direction, sometimes called mode or note order, decides the sequence. Up plays the held notes from lowest to highest and repeats. Down is the reverse. Up-down climbs and then descends, and synths differ on whether the top and bottom notes repeat at the turn. As-played uses the order you pressed the keys in, which is the one to use when you want a specific melody from a chord. Random picks freely and is better for texture than for hooks.

Rate is a note division locked to the song tempo: 1/4, 1/8, 1/16, 1/32, with triplet and dotted versions on most. At 120 BPM, 1/8 gives you four notes a second, 1/16 gives eight and 1/32 gives sixteen. Sixteenths at 120 to 130 BPM is the classic setting, fast enough to blur into a texture but slow enough that each note still registers as a pitch.

Octave range extends the pattern. At one octave the arp cycles through the notes you hold. At two it plays them, then plays them again an octave up, then starts over. Three and four are there for climbing, cinematic runs. Ward’s description of the early hardware still holds: “A ‘Range’ control sets the group of notes to be replayed over one, two or three octaves.”

Latch, also called hold, keeps the pattern running after you take your hands off. It is what lets you play an arp with one hand and reach for a filter with the other. On many synths a latched arp also transposes when you tap a new key, so one finger can move the whole pattern around the song.

Gate sets how much of each step the note actually sounds. At 50 per cent each note stops halfway to the next, which reads as staccato and tight. At 100 per cent the notes run into each other. The difference matters more than it looks: a short gate with a snappy envelope is a pluck, and a long gate with a slow envelope is a wash, from the same notes at the same rate.

How do I turn on an arpeggiator?

On most synths and DAWs the arpeggiator is a button or a switch labelled Arp, and it is off until you turn it on. Once it is running, hold a chord and it plays.

A specific walkthrough, on the one synth most iPhone owners already have. Open GarageBand for iPhone, pick a Keyboard sound, and tap the Arpeggiator button. Apple’s guide says the rest: tap the Run switch to turn it on, then set Note Order, Note Rate and Octave Range. While the arp is on, the Sustain control becomes Latch. Set Note Order to Up, Note Rate to 1/16 and Octave Range to 2, then hold C, E flat and G. That is a C minor chord, and you now have six notes cycling eight times a second: C, E flat, G, then the same three an octave up.

Then count the notes against the bar. Six notes in a bar of sixteen sixteenths does not divide evenly, so the pattern drifts against the beat and only lines back up every three bars. Add a fourth note (a B flat, for C minor 7) and drop the range to one octave, and the four-note cycle lands on every beat. Whether you want the drift or the lock is a musical choice, but you should be making it, not discovering it.

In Logic Pro the same thing is a MIDI effect called Arpeggiator, on the channel strip above the instrument. In Ableton Live it is a MIDI effect of the same name, dragged in front of the instrument. Both add controls the phone lacks, including gate length and a step pattern.

What is the difference between an arpeggiator and a sequencer?

An arpeggiator plays notes you are holding right now. A sequencer plays notes you programmed earlier. The arp needs your hands on the keys, or a latch, and it follows whatever chord you give it. The sequencer runs on its own and plays the same thing regardless of what you do.

That makes them useful for different jobs. A sequencer can hold a bassline with rests, accents and a specific melodic shape that no chord contains. An arpeggiator cannot do that, but it can follow a chord progression live, without reprogramming, because the pattern is derived from the chord rather than stored. Ward’s article describes the arpeggiator as the thing that “solved the problems of real-time control” the early step sequencers had, letting a player “change chords or time signature at will.”

The classic confusion is Donna Summer’s “I Feel Love”. The bassline pulses like an arp, but it came from a Moog modular sequencer. The notes were programmed, not held. If the pattern has a shape a chord could not produce, it is a sequence.

Donna Summer, I Feel LoveA sequencer, not an arpeggiator. Compare the shape of the bassline to the arps above.

Why producers use arpeggiators

Producers use arpeggiators for two things: to put movement on a sound that would otherwise sit still, and to play patterns too fast or too even for a hand.

A pad is a chord that sustains. It is beautiful and it goes nowhere. Run the same chord through an arp at sixteenths and it becomes a pulse that carries the track, with the harmony intact. Nothing about the notes changed; only the timing did. That is why arps are all over synthwave, trance and film scores. They create motion without a melody.

The second reason is speed. A four-octave run at thirty-second notes is not playable, and even sixteenths at 128 BPM will not stay even for eight bars under most fingers. The arp does not drift. It also lets one performer hold a chord and turn a knob at the same time, which is where most of the interesting arp sounds come from: the pattern stays constant while the filter or the LFO changes underneath it.

Which synth has the best arpeggiator?

There is no best one, because the five controls above are the same everywhere and the sound comes from the synth behind them, not from the arp. The question to ask is which features you need.

If you want the classic sound, the arps on Roland’s Jupiter-8 and Juno-60 and Korg’s Polysix offered little more than up, down, up-down and a range switch, and those settings cover most of the records in the next section. If you want to shape the pattern, look for gate length, a step pattern editor, swing and a chord memory, which the Logic and Ableton MIDI effects have and most hardware from the 1980s did not. If you want it on your phone, GarageBand’s is free and has the three controls that matter.

Where arps show up in records you know

The opening riff of Duran Duran’s “Rio” is an arpeggiator. So are the intro to Erasure’s “Fingers and Thumbs” and the riff that opens the Human League’s “Tell Me When”. All three are named in Ward’s 1996 article as typical arp parts, and all three are the same idea: a chord, played up and down, faster than a hand.

Duran Duran, RioListen for the arp under the intro, before the vocal.

Erasure, Fingers and Thumbs (Cold Summer’s Day)The opening riff is the arpeggiator.

The Human League, Tell Me WhenArpeggiated riff from the first bar.

The most recognisable arp of the last decade is the Stranger Things theme. Michael Stein told Sound On Sound in 2017 that “the Oberheim SEM Two Voice carries the main arpeggio line within the title sequence.” Listen for it: the pattern climbs and falls, the chord underneath barely moves, and the whole thing runs at a rate no one is playing by hand.

Stranger Things, Title sequenceThe main arpeggio line is an Oberheim SEM Two Voice.

Once you know the sound you will hear it everywhere. A synth part that runs at a perfectly even sixteenth-note pulse, follows the chords exactly, and never has a rest is almost always an arp. The producer held a chord. The machine did the rest.

An arpeggiator is the fastest way to make a static sound move. It is not the only way, and it is not the deepest. The pattern it plays is only as interesting as the sound underneath it, and that sound is built from an oscillator, a filter and an envelope, the same as any other. Two oscillators detuned against each other is where most of them start.