metronome [1]

Spring-activated pendular instrument whose beats can be synchronized with the tempo of a piece of music while practicing.

sliding weight

Adjustable weight that is moved along the pendulum bar to regulate the frequency of the beats.

tempo scale

Scale calibrated to a number of beats per minute (40 to 208) and used to match the tempo of a given piece of music (adagio, allegro, vivace and so forth).

pendulum bar

Metal rod that oscillates from one side of an axis to the other to produce a sound signal.

case