Here you go. I think this is what you need. WvIn seems quite simplistic compared to SndBuf. I can't really see why anyone would use it.

Kas.

(control parameters)

.read - ( string , WRITE only ) - loads file for reading
.chunks - ( int, READ/WRITE ) - size of chunk (# of frames) to read on-demand; 0 implies entire file, default; must be set before reading to take effect.
.samples - ( int , READ only ) - get number of samples
.length - ( dur, READ only ) - get length as duration
.channels - ( int , READ only ) - get number of channels
.pos - ( int , READ/WRITE ) - set position ( 0 < p < .samples )
.rate - ( float , READ/WRITE ) - set/get playback rate ( relative to file's natural speed )
.interp - ( int , READ/WRITE ) - set/get interpolation ( 0=drop, 1=linear, 2=sinc )
.loop - ( int , READ/WRITE ) - toggle looping
.freq - ( float , READ/WRITE ) - set/get loop rate ( file loops / second )
.phase - ( float , READ/WRITE ) - set/get phase position ( 0-1 )
.channel - ( int , READ/WRITE ) - sel/get channel ( 0 < p < .channels )
.phaseOffset - ( float , READ/WRITE ) - set/get a phase offset
.write - ( string , WRITE only ) - loads a file for writing ( or not )