Polyphonic vs Channel Aftertouch: Test It in Your DAW

Would you hear one finger move the filter?

Picture a held C-E-G chord where you lean on the E and only the E gets brighter, while the C and G sit still. Is that a different instrument or a party trick? You can find out in your own DAW before spending anything.

The prompt is a forum thread titled "Behringer Polykeys 61: an open-source MIDI keyboard controller with polyphonic aftertouch," started on November 2, 2026 (audiosex.pro thread). The thread shows a title and a list of related threads. It gives no price, release date or specs, and it is a forum post, not a manufacturer announcement. Treat the product as unconfirmed and don't guess about it. The question underneath is answerable today.

The MIDI difference in plain terms

Channel pressure sends one pressure value for the whole MIDI channel. It doesn't say which key you are pressing, so every note on that channel gets the same value.

Polyphonic key pressure sends a value together with a note number, so each held key carries its own pressure stream. In the MIDI 1.0 spec these are separate messages: channel pressure has one data byte, and polyphonic key pressure has two (note and pressure).

There is a catch that matters before you buy. A controller can send poly pressure, but the synth or plugin has to listen for it and offer it as a modulation source. Support varies by instrument, and a DAW can also filter or convert the data on the way through. That is why the test below checks the whole chain, not just the keyboard.

Step 1: Build the test patch

Use any synth you own that accepts pressure as a modulation source. Start from an init patch and keep it boring, because anything extra blurs what you are listening for.

1. Oscillator: one sawtooth, or two saws detuned slightly. A simple pad works too.
2. Filter: low-pass, 24 dB slope if you have the choice, cutoff around 30 percent so the chord starts dark, resonance around 20 percent.
3. Amp envelope: attack about 30 ms, sustain at full, release about 400 ms.
4. Effects: switch off reverb, delay, chorus and any drive. They smear the per-note movement.
5. Other modulation: remove velocity-to-cutoff, velocity-to-volume and mod wheel assignments, so pressure is the only thing moving.

These numbers are starting points, not a recipe. If the filter sweep is barely audible, lower the cutoff a little. If it sounds harsh, lower the resonance. For more on this, see more on create custom nks presets and verify recall in your daw.

Step 2: Map pressure to filter cutoff

Assign pressure to filter cutoff with a positive amount of roughly 50 percent. Keep that amount identical for both takes.

If your synth has separate sources for channel pressure and poly pressure, use one for Take A and the other for Take B. If it offers only one pressure source, check the manual to see which message it reads.

Step 3: Fix the chord and the velocity

Play or draw a C major triad in a mid-range octave, such as C3, E3 and G3. Octave labels differ between DAWs, so any mid-range C-E-G is fine. Hold it for eight bars.

Set every note to the same velocity, around 90, using your DAW's velocity tool or a fixed-velocity MIDI effect. Different velocities would change brightness and loudness and contaminate the comparison.

Step 4: Record two takes with matching pressure

The cleanest test uses the same pressure curve in both takes. If your DAW lets you draw pressure data, draw a ramp from zero to about 100 across bars 3 to 6 and back down across bars 7 and 8.

1. Take A, channel pressure: draw the ramp as channel pressure. All three notes receive it.
2. Take B, poly pressure: draw the same ramp as polyphonic key pressure on the E only.

DAWs differ in how well they edit poly pressure, so check the manual. If yours can't, a controller that sends it can fill the gap: press only the E, with the same gesture, for Take B. Hand-played takes will never match exactly, so repeat them until the gesture is close. This pairs well with go deeper on how to compare an analog synth plugin to hardware fairly.

By definition of the two messages, Take A should move the whole chord and Take B should move one note. That part is a prediction, not a result. The point of the test is to find out whether the difference matters to you.

Step 5: Level-match the takes

The filter opening on three notes will probably add more level than opening on one. That is an inference from how filters work, and it is exactly the kind of bias that makes the louder take sound better. Remove it.

1. Bounce or record both takes at the same length, then loop the same section of each.
2. Put a loudness meter after the synth and read short-term loudness (the 3-second LUFS-S reading) over the loop. Integrated loudness over the loop works too if your meter offers it.
3. Add a gain trim to the louder take until both readings sit within about 0.5 dB of each other.
4. Rename the files with neutral labels, such as X and Y. Let a friend shuffle which is which, or flip a coin and write the answer down without looking.

Listen to X and Y several times before you unblind. Write down which you prefer, and why, while you still don't know which is which.

Step 6: What to listen and feel for

Run through this checklist on each pass.

Also read: how to tell if music is ai generated: a daw ear test — background

1. Does the chord still sound like one chord, or does the moving note pull out of the harmony in a way you like?
2. Can you hear the single brightening voice on top of a steady backdrop, or does it just sound like volume?
3. Does the channel take feel more predictable because everything moves together?
4. When you play it yourself, can you shape one note without disturbing the others, or do you find yourself avoiding the gesture?
5. Would the effect survive in a full mix with drums and bass, or does it vanish?

Then ask the honest question. Does your music hold long chords or pads where one voice could lead? If you mostly play short stabs, arpeggios or single lines, per-note pressure has little time to act. In that case a channel-pressure keyboard, or none at all, likely covers you.

Step 7: Check which synths respond

The test only tells you something if your instruments listen to poly pressure. Run this check on each synth you actually use.

1. Search the manual for "polyphonic aftertouch," "poly pressure" or "key pressure." Note whether it is a listed modulation source.
2. Open the modulation matrix and see if there are separate entries for channel and poly pressure.
3. Put a MIDI monitor on the track and confirm what your current keyboard sends. Poly pressure messages appear as a separate type, with a note number attached.
4. Route the pressure to filter cutoff as above and see whether the sound responds to Take B only on the E.
5. If nothing happens, check whether the DAW or a MIDI filter is converting or dropping the data.

Write down the results as a short list: synth, supports poly pressure yes or no, how it is mapped. That list is the real buying guide. If most of your instruments say no, a poly-capable controller gains you very little today.

What to expect next

The Polykeys 61 thread has no confirmed price, release date or specs, so wait for an official announcement before drawing any conclusions about that board. In the meantime, keep your two blind-labeled takes and your support list. When pricing and features do appear, you will know what the feature would need to do for your music, and which of your synths would use it.