StepPolyArp Unit A Polyphonic, Polyrhythmic MIDI Arpeggiator & Step Sequencer

Developer Laurent Colson has introduced StepPolyArp Unit – a real-time polyphonic and polyrhythmic MIDI step arpeggiator and step sequencer for iOS.

It can be used as a standalone application or an Audio Unit MIDI effect plug-in.

The application and the plug-in can operate as a step arpeggiator by automatically generating melodic patterns from played notes or chords, or as a step sequencer that doesn’t require MIDI input to play.

Unlimited presets can be saved on a local device and synchronized to iCloud. Each preset contains 16 patterns, 5 customizable polyrhythmic step controllers, and a 32 steps event matrix with 11 polyphonic and polyrhythmic lines driving the arpeggiator engine.

The application supports full internal and external MIDI connections for input and output, Audiobus MIDI sender, MIDI filter routing, Ableton Link sync, and MIDI clock source sync. An internal sound bank is included.


  • Standalone application and Audio Unit MIDI effect plug-in
  • Arpeggiator and step sequencer mode
  • 1 to 32 steps programmable matrix
  • 11 configurable transposition lines
  • Polyrhythmic lines
  • 16 patterns by preset
  • Automatic chaining patterns
  • 8 octaves resizable keyboard
  • Multitasking
  • Sample-accurate timing
  • Internal sound bank
  • Tap tempo
  • Receiving MIDI from external MIDI sources
  • Receiving external MIDI sync (MIDI clock)
  • Ableton Link support
  • Internal routing of inputs, outputs, and MIDI sync
  • Send MIDI to a virtual port that can be used as MIDI input by other “Core MIDI” compatible applications
  • Default velocity, modulation, pan, volume, aftertouch, and pitch bend steps controller
  • Customizable steps controller MIDI setup
  • Arpeggiator and sequencer conform to the selected scale
  • 6 arpeggiator modes
  • 1 random mode
  • 1 chord mode
  • Random patterns creation
  • Presets manager
  • “Program Change” support
  • Native iCloud support
  • “Files” application support
  • Full support of “Split View” and “Slide Over”
  • 128 Undo / Redo levels
  • Copy and paste
  • Lockable keyboard (latch mode)

The Audio Unit MIDI effect plug-in supports multiple instances. A compatible host is required to run the plug-in. The host needs to support the Audio Unit MIDI effect format.

Compatible hosts supporting Audio Unit MIDI effect include:

  • Cubasis
  • AUM

Supported MIDI connections:

  • Virtual “Core MIDI” connections between applications
  • iOS compatible MIDI interface
  • MIDI over Wifi
  • MIDI over Bluetooth
  • Ableton Link (sync and transport)
  • Audiobus (MIDI, transport, state saving)

Pricing and Availability

StepPolyArp Unit is available now for US $14.99.

6 thoughts on “StepPolyArp Unit A Polyphonic, Polyrhythmic MIDI Arpeggiator & Step Sequencer

  1. Been intrigued by the standalone, iPad-only version for a while (same with ChordPolyArp). This universal AUv3 release sealed the deal, for me. Bought it instantly, and been having fun on both iPhone and iPad.

    As others have said (elsewhere), it’s a nice complement to the Rozeta suite by Bram Bos. In fact, it sounds like Bram opened up the field with his AU MIDI plugins, which could supersede Audiobus MIDI filters (the beta version of AB3 supports AU MIDI). Apart from the MIDIflow suite, there haven’t been that many AB MIDI filters. But these new AU plugins supporting MIDI can really make a difference as they’re supported in more contexts. In AUM, for instance, it becomes relatively easy to manage a MIDI-based workflow with plugins communicating with one another. It becomes an interesting alternative to the monolithic DAW.

    Along with SynthMaster One and the beta version of iLep, Laurent’s release made yesterday a pretty good day for one particular iOS musicker.

  2. I have bought the normal version a few weeks ago what a shame now I have to repay to get audio unit 🙁

    1. Similar situation, I bought couple of months ago. If I had known this release was pending I would have waited.

  3. Why is this a new app?

    They should make clear, too, what’s changed in this version, other than AU support.

  4. Don’t like that this is separate app from original, but I bought that 3 years ago and this is huge improvement / advancement. So, it’s important to support the developer, even though I’ll never use the original again. Downloaded last night was sequencing 5 different tracks with 1 instance in AUM. Multiple instances = mind-blowing possibilities.

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