(* Here's my code. It generates a tone with a fundamental frequency of 1000Hz
and a simple decaying envelope. The sliders can create complex beating
patterns by adding up to four more tones slightly detuned from the
fundamental and the first harmonic. *)

Manipulate[
 S = Play[
   Sin[(Sin[1000 (t + 4)] + Sin[(1000 + a) (t + 4)] +
        Sin[(1000 + b) (t + 4)])/(t + 15)^3] +
    Sin[(Sin[500 (t + 4)] + Sin[(500 + x) (t + 4)] +
        Sin[(500 + y) (t + 4)])/(t + 15)^3], {t, 0, 10},
   SampleRate -> 1000, SampleDepth -> 1];
 S, {a, 0, 50}, {b, 0, 50}, {x, 0, 50}, {y, 0, 50}]