MIDI aftertouch not recognized? What to test

You press a key, hold it, and push down harder, but your instrument does not respond. The cause could be the keyboard, a setting, the browser, or the software receiving MIDI.

Test the controller outside your music software first. The MIDI Test can show incoming MIDI messages, helping you find out whether pressure data leaves the keyboard at all.

Test whether the keyboard sends aftertouch

Open the MIDI Test in a supported browser. It does not work in Safari.
Connect and turn on the MIDI keyboard. If the browser asks for MIDI access, allow it. Choose the keyboard as the input if the test offers a device list.
Press and hold one key at a comfortable force. While keeping the key down, press it more firmly, then release it. Aftertouch is pressure sent after a key is already down, so pressing harder before the key registers is not the same test.
Watch the incoming message display while you vary the pressure. Look for channel pressure, also called channel aftertouch, or polyphonic key pressure, sometimes called poly aftertouch. The value should change as you press and release.
Repeat with a few keys, then test the keyboard in your music software. Note whether the test sees pressure messages and whether the software reacts to them.

Some keyboards require a firm push before they send pressure data. Use a moderate force and avoid pressing hard enough to strain the key. If your keyboard has an aftertouch setting, make sure it is enabled before testing.

What the result means

Pressure messages appear and change as you press

The keyboard is sending aftertouch and the browser is receiving it. If your music software still does nothing, check the instrument or track mapping. The receiving instrument must have a sound parameter assigned to pressure, such as vibrato or filter movement. A keyboard can send aftertouch correctly even when the current patch does not use it.

No pressure message appears, but notes do

The browser can see the keyboard's ordinary note messages, but it did not receive aftertouch during that test. The keyboard may not support aftertouch, it may be disabled, or the pressure sensor may not be responding. Confirm the model's specifications: some controllers have no pressure sensing, and others support only one type.

The test shows pressure, but the value does not change

The device may send a fixed value, or you may not be reaching its pressure threshold. Try a different key and vary pressure gradually while holding it down. If the same value persists across keys, check the controller's settings or test it with its manufacturer's utility.

No MIDI input appears at all

This is not yet evidence of an aftertouch fault. The browser may not have access, the keyboard may not be connected as a MIDI device, or the browser may not support the test. Check whether ordinary key presses appear before diagnosing pressure specifically.

How to fix it

Confirm the keyboard supports aftertouch. Check the model's manual or specifications for channel aftertouch or polyphonic aftertouch. A pressure-sensitive keybed is not included on every MIDI controller.
Enable pressure in the keyboard settings. Look for aftertouch, pressure, or transmit settings in the controller's menus or configuration utility. If the device has editable MIDI assignments, check whether pressure is set to send as a standard aftertouch message or as a configurable control.
Reconnect the keyboard directly. Unplug and reconnect the USB cable, try another USB port, and avoid a hub while troubleshooting. For a keyboard using a five-pin MIDI connection, check both the MIDI output and the interface input.
Allow MIDI access in the browser. Use a browser that supports the MIDI test, such as Chrome or Edge, and grant access when prompted. If you previously blocked access, open the browser's site permissions from the icon beside the address bar, change the MIDI permission if available, and reload the page. Safari is not supported by the MIDI Test.
Check that the operating system sees the device. In Windows 11, right-click Start and open Device Manager, then check whether the keyboard or MIDI interface appears without a warning symbol. On macOS, open Applications › Utilities › Audio MIDI Setup and check whether the device is listed. If it is missing, reconnect it or install the manufacturer's driver where required.
Check the track and instrument mapping. In your music software, select the correct MIDI input and make sure the track is armed or receiving input. Then choose an instrument or patch that responds to aftertouch, or assign pressure to a parameter. The assignment varies by software and instrument.
Restart and retest one change at a time. Close music software that may be holding the device, reload the browser test, and try again. If the test still receives notes but never pressure, compare with another computer or a known working keyboard before concluding the pressure sensor is faulty.

When the keyboard may be faulty

If the manual confirms aftertouch support, the feature is enabled, and no pressure messages appear on more than one computer, a failed sensor or a hardware problem becomes more likely. Test several keys, because damage can affect only part of the keybed. Save your test results and contact the manufacturer or a repair shop, especially if the keyboard is under warranty. Do not open it if doing so could void that warranty.

Channel aftertouch and poly aftertouch are different

Channel aftertouch sends one pressure value for the whole MIDI channel. Pressing harder on one held key can affect a sound shared by other held notes. Polyphonic aftertouch sends pressure for individual keys, so separate notes can affect the instrument independently. A controller may support one type but not the other, and a software instrument may respond to one type but ignore the other.

Also distinguish pressure from velocity. Velocity is normally sent when you first press a key. Aftertouch is sent while the key remains held and you change the pressure. Seeing a strong note velocity does not prove that the keyboard supports aftertouch.