Drums and percussion instruments keep the beat. A metronome keeps the beat but is not played by anyone and is not considered an instrument.
metronome
The drum is said to be a dead-beat instrument. This is because many people believe that it is over used.
Your eardrum.
Barographs
A rhythm instrument is an instrument that produces a beat, like a drum.
A drumstick
The instrument used to set the beat in music is called a Metronome.
You have to beat the Cianwood gym
the banjo
To beat (with an instrument)
It is a stethoscope.