I am confused. The man page for sox lists what appears to be an effect called pick in which you provide it with a channel number from 1 to 4 or a -l or -r flag to select either left or right audio to feed to the output file. After getting complaints from sox, I listed the -help output and got: sox: Known effects: avg band bandpass bandreject chorus compand copy dcshift deemph earwax echo echos fade filter flanger highp highpass lowp lowpass map mask pan phaser pitch polyphase rate resample reverb reverse silence speed stat stretch swap synth trim vibro vol no pick. The manual contains the following passage: phaser gain-in gain-out delay decay speed < -s | -t > pick [ -1 | -2 | -3 | -4 | -l | -r ] pitch shift [ width interpole fade ] polyphase [ -w < nut / ham > ] Is this something peculiar to the Debian distribution for sox or what? Am I just misunderstanding the instructions and trying to use pick in the wrong way? Thank you. Martin McCormick WB5AGZ Stillwater, OK OSU Information Technology Division Network Operations Group