Synths and keyboards: test every key, pad and control

Play every key from soft to hard and listen for abnormal velocity response or notes that fail to trigger. If the model supports aftertouch, test it across several areas of the keyboard.

Also check:

• pads;
• pitch bend and modulation controls;
• encoders;
• faders and pots;
• buttons;
• display and touchscreen.

A quick musical test can easily miss one defective key. A systematic scan of the control surface is much more reliable.

If some behaviour depends on the current patch, use several sounds so you do not confuse specific programming with a hardware problem.