StepPolyArp vs Atom | Piano Roll 2
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
StepPolyArp
This app functions as a real-time polyphonic and polyrhythmic MIDI step arpeggiator and sequencer. It can generate melodic patterns from input or operate as a standalone sequencer. Save and sync unlimited presets with iCloud, featuring extensive customization for patterns and step controllers.
- Standalone app and AUv3 MIDI effect plugin
- Arpeggiator and step sequencer modes
- Programmable step matrix with transposition lines
- Polyrhythmic step controllers
- Internal sound bank
- Ableton Link and MIDI sync support
- Unlimited preset saving with iCloud sync
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"StepPolyArp" is a real-time polyphonic and polyrhythmic MIDI step arpeggiator and step sequencer. It can be used as a standalone application or as an AUv3 MIDI effect plug-in. The application and the plug-in can operate as a step arpeggiator, automatically generating melodic patterns from played notes or chords, or as a step sequencer that does not require MIDI input to play. Unlimited presets can be saved locally and synchronized with iCloud. Each preset contains 16 patterns, 5 customizable polyrhythmic step controllers, and a 32-step 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, Ableton Link synchronization, and MIDI clock synchronization. An internal sound bank is included. The AUv3 MIDI effect plug-in supports multiple instances. A compatible host is required to run the plug-in. The host must support the Audio Unit v3 (AUv3) MIDI effect format. Hosts supporting AUv3 MIDI effect on iOS: Logic Pro, Cubasis, Beatmaker, AUM, Audiobus, NanoStudio, Auria Pro, apeMatrix. Hosts supporting AUv3 MIDI effect on macOS: Logic Pro 10.7 or later. Features: • Standalone application and AUv3 MIDI effect plug-in • Arpeggiator and step sequencer mode • 1 to 32-step programmable matrix • 11 configurable transposition lines • Polyrhythmic lines and clock dividers per line • Mute by line • Gate, velocity, probability, random pitch, random gate, and random velocity per event • 16 patterns by preset • Automatic pattern chaining • 8-octave resizable keyboard • Multitasking support • Stop "Audio Background" automatically after inactivity (15 min, 30 min, 1 h, 2 h, or never) • 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 usable as MIDI input by other "Core MIDI" compatible apps • Default velocity, modulation, pan, volume, aftertouch, and pitch bend step controllers • Customizable MIDI setup for step controllers • Arpeggiator and sequencer can conform to the selected scale • Predefined scales and possibility to create custom scales • 6 arpeggiator modes • 1 random mode • 1 chord mode • Randomization panel for generating random patterns with a large number of parameters to control the result • Preset manager with support for in-app purchase packs • "Program Change" support • Preset sharing via "AirDrop", "Mail", "Messages", and other supported services • Native iCloud support • "iCloud Drive" support in the "Files" app on iOS and "Finder" on macOS • Full support of "Windowed Apps" mode on iPad • Undo/Redo • Lockable keyboard (latch mode) Supported MIDI connections: • Virtual "Core MIDI" connections between applications • Any compatible MIDI interface • MIDI over Wi-Fi • MIDI over Bluetooth • Ableton Link (sync and transport)
Atom | Piano Roll 2
This advanced AUv3 MIDI editor and sequencer allows for complex musical composition and live performance. It functions as a plugin within compatible music hosts, enabling users to create intricate patterns, launch clips, and customize workflows with scripting.
- AUv3 MIDI note editor
- Modular sequencer
- Clip launcher
- Step input and real-time recording
- Customizable layouts and themes
- Scripting for custom workflows
- Ghost lanes for harmonies and counterpoint
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Reached #1 on the App Store in the Top Paid Music App Category. The most advanced AUv3 MIDI note editor, modular sequencer and clip launcher on iOS. Notes: - This plugin does not run as a standalone app and requires a compatible host. - MIDI is not sound. To make sound you'll have to feed the MIDI into a synthesizer or instrument app. Bring your own synths! - Hardware integration with controllers requires iCloud Drive. Compatibility: - Special integration with hosts: AUM and Drambo. - Tested hosts: ApeMatrix, Audiobus, BeatMaker, Cubasis, MTS, Zenbeats. Limited support by NanoStudio 2. Not supported by GarageBand. Build live sets for clip launching, or an entire track with unlimited length. Play the whole sequence, or adjust the loop markers to iterate over a single section. Step input, or record as played, all with perfect timing accuracy. Write your own code, share it with the community! You can control hardware devices, adding support for new controllers or completely changing the behavior of existing ones. Build your own styling with custom layouts and themes. Change colors, fonts, sizes… make it yours! Piano Roll 2 takes all the features you love about the first installment, and expands them into an entirely new breed of modular sequencer and clip launcher, unparalleled in flexibility and depth on iOS. We redesigned it from the ground up to incorporate a plethora of new features and workflows. - It's a sequencer that augments the capabilities of your host or DAW. - It's a composition tool that helps you to write beautiful melodies and complex polyrhythmic patterns. - It's a clip launcher that integrates seamlessly with supported hardware controllers. - It's a scripting playground that lets you customize your workflow with code. - It's a swiss-army knife of possibilities when working with MIDI. Here are just some of the many use cases this modular architecture supports: - Build live sets for clip launching. - Compose patterns with touch, Apple Trackpad and Apple Pencil, or use the step input mode to write melodies step-by-step. - Capture performances in real time and export your patterns as MIDI files. - Import and edit MIDI files created in other apps, or from commercial packs. - Record generated MIDI of other plugins or sequencers. - Write harmonies and counterpoint melodies by superimposing the patterns of other Atoms as ghost lanes. - Construct complex polyrhythms by taking advantage of custom time signatures and grid fractions. - Sequence the sequencers for full modular mayhem.
Screenshots
Verdict
The clearest difference is in-app purchases: Atom | Piano Roll 2 at none against StepPolyArp's 2. Atom | Piano Roll 2 also leads on update cadence (weekly vs every 2 months) and iOS requirement (12.1 vs 15.0). StepPolyArp's advantage is rating (4.8 vs 4.5) and review sentiment (87% vs 68%). On price, ratings volume, ads and monetization model there is nothing between them.
Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS
StepPolyArp costs $19.99 and Atom | Piano Roll 2 $19.99 up front. StepPolyArp sells 2 one-off in-app purchases. Atom | Piano Roll 2 asks for nothing beyond the download.
StepPolyArp holds the better App Store score, 4.8 against 4.5. Both are backed by a comparable volume of ratings — 48 and 96 respectively. Written reviews point the same way: 87% of StepPolyArp's written reviews are positive against 68% of Atom | Piano Roll 2's.
StepPolyArp ships an update every 2 months, Atom | Piano Roll 2 weekly. Both last shipped on October 19, 2026.
| Parameter | StepPolyArp | Atom | Piano Roll 2 |
|---|---|---|
| Price | $19.99 | $19.99 |
| Rating | 4.8 (48 ratings) — better | 4.5 (96 ratings) |
| Positive reviews | 87.0% of reviews — better | 67.5% of reviews |
| Number of ratings | 48 | 96 — better |
| Update frequency | Every 2 months | Weekly — better |
| Ads | No | No |
| In-app purchases | Yes | No — better |
| Monetization | Paid | Paid |
| Devices | iPhone, iPad, iPod, Mac — better | iPhone, iPad, iPod |
| Requires iOS | 15.0 | 12.1 — better |
| Further details — not scored | ||
| Size | 38 MB | 16 MB |
| Age rating | 4+ | 4+ |
| Developer | Laurent Colson | Victor Porof |
Customer experience
StepPolyArp
Atom | Piano Roll 2
Bugs and requests
StepPolyArp
Not enough reviews yet to summarise bugs or requests.
Atom | Piano Roll 2
Reported bugs
13 issues- Crashes when saving sessions in AUM
- Notes get corrupted during playback
- White background display issue
- Position indicator jumps when loop doesn't start at bar 1
- Buttons for adding bars disappear after certain point
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- MIDI input processed incorrectly even in passthrough mode
- Notes don't play after being added to piano roll
- App doesn't appear in AU list on MacBook Pro
- Launchpad Pro MK3 session clip launch mode not working
- iOS 12 compatibility crashes
- Incompatibility with Cubasis 3 and GarageBand
- Responsiveness issues with Apple Pencil (resolved in updates)
- GUI rendering problems on some iPad models
Requested features
17 requests- MIDI CC editing and visualization
- Mouse and trackpad input support
- Logic Pro for iPad support
- Chord entry in step input mode
- Velocity editing improvements and visual feedback
Show 12 moreShow fewer
- Dark mode option
- Drag and drop from Suggester
- Time stretch/MIDI stretch functionality
- Standalone mode without requiring AUM
- Launchpad Pro MK3 full compatibility
- Grid-style interface similar to Launchpad
- Step input for multiple notes simultaneously
- Better zoom and selection for longer patterns
- Undo last recording feature
- Parameter automation curves
- Easier MIDI channel switching
- Tutorials and documentation
In-app purchases
StepPolyArp
- Dance Horizons$4.99
- Analog Sequence$4.99
Atom | Piano Roll 2
No in-app purchases
Questions
Is StepPolyArp free?
Is Atom | Piano Roll 2 free?
Which has better reviews, StepPolyArp or Atom | Piano Roll 2?
Do StepPolyArp or Atom | Piano Roll 2 have ads?
Which is updated more often, StepPolyArp or Atom | Piano Roll 2?
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