How do I change the rhythmic dictation instrument from snare to something sustained?

[Edje]

The default, snare, is useless because it doesn't allow you to hear note duration.

I want to change it to something like cello.

I tried Tools - Midi - Midi Instruments - Percussion - Rhythms - change channel/preset/note/use .wav file
but nothing changed.

[Quentin]

Hello,
This is an option that you will find in the Exercise Settings menu at the top of the screen. The option is called "Evaluate Note Length". When that option is selected, EarMaster uses a piano sound and evaluates not only the timing but also the duration of the rhythmic note values you play.