Beats
The beats are the units in our System of Measurement,--as it
were, the inches upon our yardstick of time; they are the particles of
time that we mark when we count, or that the conductor marks with the
beats of his baton. Broadly speaking, the ordinary beat (in moderate
tempo) is about equivalent to a second of time; to less or more than
this, of course, in rapid or slow tempo. Most commonly, the beat is
represented in written music by the quarter-note, as in 2-4, 3-4, 4-4,
6-4 measure. But the composer is at liberty to adopt any value he
pleases (8th, 16th, half-note) as beat. In the first study in
Clementi's Gradus ad Parnassum, the time-signature is 3-1, the whole
note as beat; in the 8th Sung Without Words it is 6-16, the sixteenth
note as beat; in the last pianoforte sonata of Beethoven (op. 111),
last movement, the time-signatures are 9-16, 6-16, and 12-32, the
latter being, probably, the smallest beat ever chosen.