1) Amplitude modulation (AM) varies the amplitude of a carrier wave according to the amplitude of a modulating signal. This generates sideband frequencies above and below the carrier frequency. 2) The sidebands are softer than the carrier and produce an effect like overtones or subtones, making them useful for timbre construction. More complex modulating signals produce more sidebands. 3) In an example where a 1,000 Hz carrier is modulated by a 100 Hz signal, the results are signals at 1,000 Hz (the carrier) as well as 1,100 Hz and 900 Hz (the upper and lower sidebands).