The world of alternate firmware for synths is rapidly expanding – and it’s bringing new features to synths that are still in production.

The latest example is prophet-rev4-mods, a free alternate firmware for the Sequential Prophet-5 and Prophet 10 Rev4 line that adds an arpeggiator, polyphonic step sequencer, octave shifting and patch-level sequence memory.

The project is designed to expand the Rev4’s performance capabilities without requiring hardware modifications.

Features:

• Adds an arpeggiator to the Sequential Prophet-5 Rev4 and Prophet-10 Rev4 firmware.
• Offers Up, Down, Up/Down, Random and Assign arpeggiator modes.
• Supports arpeggiator patterns spanning one to four octaves.
• Provides adjustable tempo from 40 to 300 BPM, with both knob control and tap tempo.
• Supports external MIDI clock synchronization.
• Offers a range of note divisions, including dotted, triplet and swing settings.
• Includes a HOLD latch with re-latch behavior for changing held notes or chords.
• Adds a polyphonic step sequencer with up to 512 steps.
• Sequences chords of up to 10 notes, retaining the velocity of recorded notes.
• Supports rests and ties, along with recording from the keyboard or MIDI input.
• Provides forward, backward and pendulum playback directions.
• Allows sequences to be transposed from the keyboard.
• Can route a recorded chord sequence through the arpeggiator, turning it into a changing chord progression.
• Adds a front-panel keyboard octave shift of plus or minus two octaves, also affecting arpeggiator operation and MIDI output.
• Saves arpeggiator settings and recorded sequences with user programs.
• Uses existing front-panel controls rather than adding external controllers or modifying the hardware.
• Can be bypassed at startup, allowing the synthesizer to operate with its standard behavior when the patch is inactive.
• Applies to the official Main OS 2.1.0 file through a browser-based patcher and installs using the standard SysEx update process.

Pricing & Availability:

The prophet-rev4-mods project is available free of charge from GitHub under the MIT license. Users need Sequential’s official Main OS 2.1.0 firmware file and a MIDI SysEx transfer utility to create and install the patched firmware. The repository provides installation instructions and a method for restoring the original official firmware.

The project is not affiliated with Sequential. The author reports testing the modification on a Prophet-10 Rev4 in October 2026, while the Prophet-5 Rev4 remains untested on hardware. Users should review the repository’s documentation, risks and recovery requirements before installing the patch.