A recurring source of confusion in expressive-synth shopping: a plugin's feature list says "polyphonic aftertouch" and "polyphonic glide", the marketing copy says "expressive" — and yet the developer's FAQ says MPE isn't supported. Both statements are true at once, and understanding why saves you a refund request.
September 2026 gave us a clean example. KeySolutions Sounds released Traveler, a cinematic hybrid synth from sound designer Mike Martin, built around virtual-analog and wavetable oscillators, modelled ladder and DW-8000-style filters, and over 400 presets from a well-known cast of designers. Its specification includes mono and polyphonic aftertouch, polyphonic glide and full MIDI CC learn. It does not currently include MPE.
That's not an oversight or a half-finished feature. They're different mechanisms.
The channel question
Polyphonic aftertouch (poly AT) is a standard MIDI 1.0 message: 0xAn, carrying a note number and a pressure value. It travels on a single MIDI channel and identifies which note it applies to by note number. Sixteen notes on one channel, sixteen independent pressure streams — no channel juggling required.
MPE takes a different route. It reserves a block of channels and assigns one channel per sounding note, so each voice gets the full set of channel-scoped messages: channel pitch bend, channel pressure and CC74 for timbre. The note is identified by which channel it's on rather than by a note number inside the message.
Both give you per-note pressure. Only one gives you per-note pitch bend.
That's the crux. Pitch bend in MIDI 1.0 is a channel message with no note number field. There is no such thing as a note-specific bend on a single channel — which is precisely why MPE exists. If you want to bend one note of a held chord while the others stay put, you need that note on its own channel. Poly AT cannot do it, no matter how well implemented.
What "polyphonic glide" usually means
Here's where terminology gets slippery. "Polyphonic glide" or "poly portamento" typically describes the synth's internal voice behaviour: when you play a new chord, each voice slides from its previous pitch to its new one independently, rather than the whole chord gliding as a block. That's a voice-allocation feature inside the instrument.
It sounds superficially like per-note pitch control, but the player isn't driving it in real time — the synth is interpolating between notes you played. Sliding your finger sideways on a Seaboard or LinnStrument won't bend that one note unless the instrument is reading per-channel bend.
The practical test
Before buying, ask one question: can I bend a single note of a held chord independently?
- Yes → the instrument reads per-note pitch bend, which in MIDI 1.0 means MPE.
- No, but pressing harder on one key changes only that note → polyphonic aftertouch.
- No, and pressing harder changes the whole chord → channel aftertouch only.
If you play an Osmose, a Seaboard, a LinnStrument, an ERAE or an Exquis, your entire technique depends on the first answer. A poly-AT synth will respond to your pressure and ignore your slides and bends — often producing a strange half-working feel that's more frustrating than no expression at all.
Why developers choose poly AT first
It's genuinely less work. Poly AT plugs into an existing per-voice modulation path: the note is already identified, so you route the pressure value to a destination and you're done.
Proper MPE support touches architecture. The plugin must parse zone configuration (which channels belong to the zone, and whether the master channel is channel 1 or 16), maintain per-channel state for bend, pressure and CC74, apply the correct pitch bend range — commonly ±48 semitones rather than the default ±2 — and handle voice stealing sanely when the controller reuses a channel. Then the preset library needs revoicing, because patches designed for a keyboard rarely map well onto three continuous dimensions.
Poly AT is also a real win for players on Polybrute 12, Hydrasynth or MODX-class keyboards with poly-pressure keybeds. It's a legitimate feature serving a legitimate audience — it just isn't ours.
What to watch for
"Expressive" in marketing copy means nothing technically. "Supports aftertouch" with no qualifier usually means channel aftertouch. "Per-note" is a good sign but check whether it covers pitch. "MPE" stated plainly is the only reliable signal, and even then it's worth asking whether the implementation is lower-zone only and how many voices it allocates.
Traveler is available at an introductory $99 (regular $149) through the end of September 2026, bundled with the KeyTime and KeySpace effects — a strong package for composers working from a poly-AT keybed. For MPE controller owners, it's one to keep on the watchlist rather than the shortlist.
Sources: SYNTH ANATOMY, rekkerd