Apercussion instrument that can play a lot of notes at a very fast tempo, and whose high timbre can be heard over the sound of the larger orchestra, is the

The xylphone is a percussion instrument that can play a lot of notes at a very fast tempo, and whose high timbre can be heard over the sound of the larger orchestra.

Explanation:

To understand this answer we need to observe the characteristics of these instruments. First, we need a high tempo percussion instrument. Well, practically almost all of them could be played at a high tempo. However, the fastest is the snare drum. Also, we have a very good characteristic here. Its sound can be heard over a large orchestra. no this discards many of percussion instruments. Leaving us with 2 options. Cymbal which is incredibly nice on surpassing the whole orchestra and the snare drum. But none of them can produce a lot of notes. So our only option would be the Xylophone and that is why it is the correct answer.