Setting up MPE is often the least glamorous part of making music with an expressive controller. Zones, bend ranges and channel counts all have to agree between hardware, host and plugin. discoDSP's OB-Xd 3.21 takes a step toward removing that friction, and it does so in a synth that is free to download. Here is what changed and how to use it.
What is new in 3.21
According to KVR's coverage, the update focuses on MPE usability:
- Automatic MPE configuration: the plugin switches MPE on or off from RPN 6 (the MPE configuration message) and reads the per-note bend range from RPN 0. It detects both Lower and Upper Zone setups.
- Multi-destination Y axis: the slide dimension (CC74) can drive several parameters at once, including pulse width, PW offset, cross modulation, oscillator 2 detune, cutoff, pitch and pan.
- Z axis default: channel pressure now defaults to amplitude, running from silence to full level.
- MPE Setup menu: found under MIDI > MPE Setup, with per-axis depth controls and a new 3-semitone bend range option.
- Live feedback: the Y and Z destination knobs show green dots that move with incoming modulation, and the display briefly shows MPE ENABLED or MPE DISABLED when the mode changes.
- MPE presets: factory patches are named after controllers such as LinnStrument, ROLI Seaboard, Sensel Morph and Haken Continuum.
The update is free for all OB-Xd 3.x customers. The plugin itself is a free download from discoDSP, with an optional $99 registration that unlocks extra features and a commercial-use license. It runs in VST, VST3, AU, AAX, LV2 and standalone formats on Windows, macOS and Linux, with standalone and AUv3 versions on iOS.
Why RPN-based detection matters
MPE controllers announce their configuration by sending an MPE Configuration Message over RPN 6, telling receivers which channels form the Lower and Upper zones. A well-behaved synth listens for that message and adapts. An older one needs you to dial everything in by hand, and a mismatch leads to the classic symptoms: every note bending together, or pitch bends that are far too wide or too narrow.
By reading RPN 6 and RPN 0 itself, OB-Xd removes two common failure points. If your controller sends the right messages on connection, the synth should simply start behaving as an MPE instrument.
A quick setup routine
- Load the plugin on a track whose MIDI input is your MPE controller. In most hosts, leave the track in standard MIDI mode and let the plugin handle channels.
- Power-cycle or re-select the controller port after loading, so it re-sends its configuration message.
- Check the display for the MPE ENABLED indicator.
- Open MIDI > MPE Setup and confirm the bend range matches your controller. Many devices default to 48 semitones; the plugin should read it automatically, but verify it by bending a note.
- Play a chord and move one finger. Only that note should change.
- Adjust the Y and Z depths until the response feels natural for your playing style.
If your host manages MPE itself, such as Bitwig Studio or Ableton Live, make sure its MPE setting and the plugin agree.
Making use of the multi-destination slide
The most musical change is arguably the Y axis. Mapping slide to cutoff and pulse width together gives a patch that brightens and thickens as you move up the key or pad. Sending it to oscillator 2 detune adds a subtle ensemble effect that opens only when you want it. Keeping depths low and layering destinations tends to sound better than pushing one parameter to its limit.
For pressure, amplitude is a safe default, but consider turning it down and routing expression elsewhere if you prefer a steady volume with filter movement.
Who benefits
This update suits anyone who wants an inexpensive, classic-sounding virtual analog voice for expressive playing, and beginners will appreciate not having to understand RPN messages to get started. Experienced players gain a reliable baseline patch to compare against newer MPE-native instruments.
Download the latest build from discoDSP and read the full KVR report for the complete change list.