"The peculiar "throbbing" heard when sounds not quite identical in pitch are sounded together." [Stainer, John; Barrett, W.A.; A Dictionary of Musical Terms; Novello, Ewer and Co., London, pre-1900]
A unit of measurement indicated by the conductor's gesture; each unit of a measure with respect to accent.
See Also
Additive and Subtractive Synthesis
Chord
Clang
constructive and deconstructive interference
difference tone
Figure 8.6 - Difference Tones
Heterodyne
Power of Beat Harmonics
Great Pyramid
Rhythm
Time