"pix/fmeq43.png" alt="wc">
and symmetrically placed sidebands 
separated by
<img src="pix/fmeq42.png" alt="wm">.  
The amplitudes follow the Bessel functions.  I put carrier in quotes because in 
computer music we listen to the result of the modulation (this was Chowning's idea &mdash; see "The 
Synthesis of Complex Audio Spectra by Means of Frequency Modulation").  The Bessel functions 
are nearly 0 until the index (B) equals the order (n).  Then they have a bump and tail off as
a sort of damped sinusoid:
