What the MIDI tester shows
Every key, wheel, fader and pedal on a MIDI controller sends a short message when you move it. The tester shows those messages as they arrive, so you can see what your hardware actually sends rather than what the manual says it sends. Notes appear on the keyboard with their velocity, and continuous controllers appear as meters and in the controller table.
Composers mostly need it for one question: is the mod wheel sending CC1, and does it reach both ends of its range? If a sample library's dynamics will not move, or stop short of fortissimo, the answer is usually here.
How to check your mod wheel
Press Connect, then Start the check and move the wheel slowly from bottom to top and back. The tester reports the controller number that moved, the lowest and highest values it reached, and whether that matches what orchestral libraries expect.
- It reports CC1 from 0 to 127. The wheel is fine. If a library still does not respond, check the library's own CC assignment and the MIDI channel.
- It reports a different controller. The keyboard is mapped to something else. Change it in the keyboard's settings or its editor software, or remap it to CC1 in your DAW.
- It stops short of 0 or 127. The wheel is worn or needs calibrating. Many controllers have a calibration routine in their manual.
New to the controller itself? Start with what a mod wheel is and what CC1 controls. For how to ride CC1, CC11 and CC21 together on strings and brass, read understanding MIDI CCs.
The controllers orchestral libraries use
| CC | Usual job |
|---|---|
| CC1 | Modulation wheel (dynamics in most orchestral libraries) |
| CC11 | Expression |
| CC21 | Vibrato in many orchestral libraries |
| CC64 | Sustain pedal |
| CC7 | Channel volume |
| CC10 | Pan |
| CC2 | Breath controller |
| CC74 | Brightness / filter cutoff |
CC1 and CC11 are close to universal. Vibrato is not standardised, and CC21 is only the most common choice, so check each library's manual. Keep CC64 off strings and brass, because a held sustain pedal breaks most legato scripts.
Velocity, pitch bend and aftertouch
Velocity is how hard each key was struck, from 1 to 127. The velocity range bar shows the softest and hardest of your last 32 notes. If you cannot reach the top or the bottom without straining, change the keyboard's velocity curve rather than the library.
Pitch bend should rest at 0 in the middle of its travel and reach about −8192 and +8191 at the ends. Aftertouch (pressure) only appears if your keyboard has it, and many libraries ignore it unless you map it.
If nothing appears
- Use Chrome, Edge, Opera or Firefox on a computer. Safari and every browser on iPhone and iPad have no Web MIDI.
- Allow MIDI access when the browser asks. Firefox installs a small site permission add-on the first time.
- Try another USB cable. Some cables only charge and carry no data.
- On Windows, close your DAW and any editor software first, then press Connect again.
- Plug the keyboard in before you press Connect, or unplug and replug it while the page is open.