sndfile - oscillator for disc files (digital recordings)

sndfile output[b] amplitude[bvpn] increment[bvpn] filename[s] channel[vpn] 
 startframe[bvpn] endframe[bvpn] pos[d] p1[d] p2[d] p3[d] p4[d] ;

Repeatedly reads in the specified channel (channels are numbered from
0) of the file named by the filename string variable, starting at
sample startframe, ending at sample endframe (if endframe = -1 then the
end of the file is used).  The specified increment is applied to the
file (this is normally 1.0); if the end of the specified segment is
reached, sndfile starts reading again from the startframe.
