The MPC arpeggiator: the complete guide to Arp, Rhythm, and Pattern

The short version

Akai's manual states it plainly: the MPC's hardware includes a full-featured arpeggiator and phrase player for melodic track types, on top of the traditional note repeat functionality that lives behind the same button. Open the window, and an Action field switches between four distinct behaviors: Arp (hold a chord, it plays a pattern built from the held notes), Rhythm (hold a chord, it plays a rhythmic pattern instead of a melodic one), Pattern (hold a single note, it triggers and transposes a pre-built melodic phrase), and Note Repeat (a second, more flexible path to plain retriggering, already covered in depth in this site's Note Repeat and 16 Levels guide). This article is the other three quarters of that window: Arp, Rhythm, and Pattern, plus the Setup, Settings, Probability, and Modifiers sections every action shares.

SAM'S NOTE: I slept on this window for longer than I want to admit, because the entry point makes it look like a Note Repeat sub-menu. Hold Note Repeat, tap Arp, done, right? Then I actually left the Action field on Arp instead of switching it to Note Repeat, held down a chord on a Keygroup track, and the thing played an actual pattern back at me built from the notes I was holding. That's a different tool wearing the same doorway.

The catch: no drum tracks

Before anything else, the one restriction that decides whether this feature is even available: the Arpeggiator only opens on melodic track types.

"To open the Arpeggiator settings: 1. Set the current track type to Plugin, Keygroup, MIDI, or CV."

Drum tracks are not in that list. That lines up with what the feature actually does, holding a chord to trigger a pattern assumes the track is set up to receive multiple simultaneous notes across a keyboard-style range, which is exactly what Plugin, Keygroup, MIDI, and CV tracks are built for and a Drum track's one-pad-one-sound layout is not. If a track is set to Drum and the Arpeggiator window won't open, or opens but the Action field won't do anything useful, that's the restriction working as documented, not a bug.

Opening the Arpeggiator window

Two ways in, both documented, both leading to the same window:

"Open the Arpeggiator window by doing either of the following: • Press and hold the Note Repeat button, then tap Arp at the bottom-right of the screen. • Alternatively, press the Arpeggiator F-Key (MPC X)."

The second method is hardware-specific: a dedicated Arpeggiator F-Key exists on the MPC X's function-key row, not on every model. Once the window is open, two toggles sit at the top regardless of which action is selected: Enable, which turns the Arpeggiator on or off, and Latch, which keeps it running without a held note or chord once triggered.

The Setup section: five shared fields

Whichever action ends up selected, five fields in the Setup section apply across all of them:

"Use the Action field to set the type: Arp, Note Repeat, Rhythm, and Pattern. Use the Time Division selector to set the note value of each arpeggiator step from 1/1 to 1/64 beats, including T (triplet) variations. This parameter is not available when Action is set to Pattern. Use the Note Length slider to set the length of the played note in each step, from 1 to 100%. Use the Velocity field to set the velocity of the arpeggiator notes. Choose As played, From first note, Accented, Full, 3/4, Half or 1/4. Use the Swing field to set the amount of swing in the arpeggiator from 50% to 75%. Swing lets you 'shuffle' your beats, from subtle to extreme."

Two details worth flagging on their own. First, Time Division is disabled outright when Action is set to Pattern, since a pre-built phrase carries its own internal timing and a step rate doesn't apply the same way. Second, Time Division is tied to the project's global Time Division setting and stops working entirely if that's been switched off. That is the same global Time Division field this site's Swing and Quantize guide covers for recorded-note quantization, and it means an arpeggiator that seems to have stopped stepping is worth checking against that global setting before assuming the Arpeggiator window itself is broken.

Arp mode: hold a chord, get a pattern

Set Action to Arp and the window's Arp mode section becomes active:

"The Arp mode section of the Arpeggiator window is available when the Action is set to Arp. When this action is selected, hold down a chord and the arpeggiator will play a pattern based on the notes held. Use the Arp Pattern field to set how the arpeggiator triggers the held notes. Use the Octaves field to set how many octaves of the held notes the arpeggiator will cycle through. Use the Variation field to apply rhythmic variation to the set pattern."

This is the mode the feature's name promises: hold three or four notes as a chord on a Keygroup or Plugin track, and instead of hearing them stacked, the Arpeggiator breaks them apart into the sequence set by Arp Pattern (Akai's manual doesn't spell out every named pattern in the field's own description, so treat the exact pattern list as something to audition on the hardware rather than something this article invents), cycles through however many Octaves are set, and layers in whatever rhythmic Variation is dialed in on top. Release the chord and, unless Latch is on, the pattern stops.

Rhythm mode: hold a chord, get a groove

Set Action to Rhythm and the same chord-hold gesture drives a different kind of output:

"The Rhythm section of the Arpeggiator window is available when Action is set to Rhythm. When this arpeggiator action is selected, hold down a chord and the arpeggiator will play the held notes in a rhythmic pattern. Use the Rhythm Pattern field to choose the pattern played when notes are held."

The distinction from Arp mode is subtle in the manual's own wording but real in practice: Arp mode's job is to unstack a chord into a melodic sequence, cycling octaves and applying variation to the pitches. Rhythm mode keeps the same held-chord trigger but is built around a rhythmic template instead, one Rhythm Pattern field rather than the three-field Arp Pattern/Octaves/Variation combination. If the goal is a syncopated stab pattern rather than a rising or falling melodic run, Rhythm is the mode built for that job specifically, not a variant of Arp.

Pattern mode: hold one note, get a phrase

Set Action to Pattern and the trigger gesture itself changes, from a held chord to a single held note:

"The Pattern section of the Arpeggiator window is available when the Action is set to Pattern. When this arpeggiator action is selected, hold down a single note to trigger a melodic phrase. As you change what note is held, the melodic phrase will be transposed. Use the Pattern field to choose the pattern."

Pattern mode is the odd one out structurally, and worth being clear about since it's easy to expect it to behave like Arp or Rhythm. It doesn't listen for a chord at all, one held note is enough. What plays back is a pre-built melodic phrase, not a sequence generated from the notes you're holding, and the only thing your held note controls is the transposition of that phrase up or down. This is also the one action where the Setup section's Time Division field goes away entirely, since the phrase's own internal timing takes over instead of a step rate.

Settings and Probability

Two more sections apply across every action. Settings covers sustain pedal behavior:

"If you have a sustain pedal connected, you can enable Sustain Pedal Latches to use it to control latching. Use the Latch Mode setting to set the action of the sustain pedal, either Reset or Add."

Probability adds a second layer of variation on top of whichever action and pattern are already selected:

"The Probability section of the Arpeggiator window lets you add further variation to your arpeggiator by adjusting the probability of how notes are played. Use the Accent (%) field to set the percent probability that a note in the arpeggio is accented. Use the Normal (%) field to set the percent probability that a note in the arpeggio is normally articulated."

In practice, this is what keeps a repeating arp pattern from sounding mechanically identical on every cycle: with Accent and Normal probabilities set below 100%, individual notes in the pattern will vary in articulation from one pass to the next, rather than hitting the exact same accent structure every single time.

Modifiers: playing the arp live

The last two sections turn external MIDI controller data into live, real-time changes to the arpeggiator's own settings, rather than fixed values you dial in once. First, which controller messages are allowed in at all:

"Tap the Channel Pressure box so it is checked to enable Channel Pressure messages from external MIDI controllers to modify the arpeggiator. Tap the Expression box so it is checked to enable Expression messages (MIDI CC #11) from external MIDI controllers to modify the arpeggiator. Tap the Aftertouch box so it is checked to enable Aftertouch messages from the pads or external MIDI controllers to modify the arpeggiator. Tap the Mod Wheel box so it is checked to enable Modulation messages (MIDI CC #1) from external MIDI controllers to modify the arpeggiator."

Then which of the arpeggiator's own parameters those enabled messages are allowed to bend, and by how much, one Max Amount field per modifiable parameter:

"Tap the Modify Time Division box... Use the Max Amount to set by how much the time division can be changed, from 1 to 4... Tap the Modify Octaves box... Use the Extra Octaves field to select how many additional octaves... can be added with the modifier control, from 1 to 4... Tap the Modify Note Length box... Use the Max Amount (%) field to select by how much percentage the note length is increased, from 1 to 100%... Tap the Modify Swing box... Use the Max Amount (%) field to select by how much percentage the swing amount is increased, from 1 to 50%... Tap the Modify Variation box... Use the Max Amount field to select by how the variation setting can be changed, from 1 to 4... Tap the Modify Probability box... Use the Max Amount (%) field to select by how much percentage the probability amount is increased, from 1 to 100%."

Stacked together, this is a genuinely deep live-performance layer bolted onto what looks at first glance like a fixed-settings pattern generator: a mod wheel push or an aftertouch squeeze on a connected keyboard can widen the octave range, loosen the swing, or bump the probability of accented notes mid-performance, all without touching the screen. None of the six modifiable parameters (Time Division, Octaves, Note Length, Swing, Variation, Probability) are on by default per the manual's own checkbox-based wording, each one is opted into individually.

The fourth action: Note Repeat

The Action field's fourth option, Note Repeat, is deliberately not re-covered here in depth. This site's Note Repeat and 16 Levels guide already breaks it down field by field, including the genuinely useful reason to reach for it over the hardware Note Repeat button: it runs on its own Time Division, Note Length, Velocity, and Swing settings, independent of the project's global Timing Correct grid, at the cost of losing the Arp Pattern, Octaves, Variation, Rhythm Pattern, and Pattern fields that make the other three actions distinct. This article picks up where that one left off, the three actions with dedicated parameter sections of their own.

A recording gotcha worth knowing

One cross-reference worth surfacing on its own, because it's easy to miss buried in the Recording section of the manual rather than the Arpeggiator chapter itself. A separate recording preference, Place Events Recorded During Count-In at Start Point, normally lets a pad hit during the pre-count land exactly at the start of the recording:

"Place Events Recorded During Count-In at Start Point: When enabled, pressing a pad during the recording's pre-count will record that note event at the start of the recording (this is how the MPC3000 worked). When disabled, no notes will be recorded until the pre-count is finished and recording has begun."

Directly beneath that field, a one-line note that's easy to skim past:

"Note: This setting is ignored when recording with the Arpeggiator active."

Practically, that means recording an arpeggiated part while pressing a chord during the count-in behaves differently than recording a normal part the same way, regardless of how that preference is set. Worth knowing before assuming a missed count-in hit is a timing mistake rather than this documented exception.

Common mistakes

Mistake: trying to open the Arpeggiator on a Drum track. The window is only available on Plugin, Keygroup, MIDI, and CV tracks. Switch the track type first.

Mistake: setting Action to Pattern and expecting a chord to change the melody. Pattern mode reads a single held note for transposition only, it plays back a pre-built phrase rather than generating one from a chord. That chord-reading behavior belongs to Arp and Rhythm modes.

Mistake: assuming the arpeggiator has stopped working when it's actually the project's global Time Division. The Setup section's Time Division field is tied to the project setting and does nothing if that's been switched Off.

Mistake: expecting a Modifier checkbox to do anything by itself. Enabling Channel Pressure, Expression, Aftertouch, or Mod Wheel only allows that MIDI message type through. It still needs at least one Modify [Parameter] box checked below it before any incoming message actually changes an arpeggiator setting.

A note on manual versions

Every technical claim above is checked directly against Akai's Standalone OS User Guide, Manual Version 3.9, cross-checked against Manual Version 3.7 and confirmed word-for-word identical in content across the Setup, Arp, Rhythm, Pattern, Settings, Probability, and Modifiers sections. The page numbers shifted by a flat five pages between versions inside the Arpeggiator window's own chapter: the section opens on page 84 in v3.9 and page 79 in v3.7, both confirmed against each version's own table of contents and by direct single-page extraction of the section's own printed footer number, with the Arp, Rhythm, Pattern, Settings, and Probability sections landing on page 85 in v3.9 (page 80 in v3.7) and the detailed Modifiers fields spilling onto page 86 (page 81 in v3.7). The recording cross-reference in this article, the count-in note tied to the Arpeggiator, sits in a different chapter entirely and shifts by only four pages, page 66 in v3.9 versus page 62 in v3.7, not five. This site's Mute Groups guide documented a non-uniform 6/8/10-page drift elsewhere in the same manual, so between that finding and this article's own 5-page-here, 4-page-there result, the size of the shift is chapter-specific and never assumed to hold at one number across the whole document.

Several quoted passages' punctuation were normalized for this site's house style: the source PDF's number ranges (for example the Setup section's "1/1 to 1/64 beats" and every Max Amount field's "1 to 4" or "1 to 100%") use an en dash character in the extracted text, rendered here in the blockquotes as spelled-out "to" ranges rather than reproduced with the source's dash character. The numbers themselves are unchanged; only the connecting punctuation was normalized. This matches the same convention already documented in this site's Mute Groups guide, which elided an identical dash-based range from its own quoted material rather than reproduce it, holding the zero-em-dash, zero-en-dash rule for shipped body copy even inside direct quotes.

Verdict

Found a modifier combination worth sharing, or a pattern preset that surprised you? Tell us what happened.