Allows the specification of an arbitrary UNIX command to play the waveform. The default audio is netaudio if it is supported. If none of these is supported, sunaudio is the default. If set to raw, this indicates that the input file does not have a header. While this can be used to specify file types other than raw, this is rarely used for other purposes as the file type of all the existing supported types can be determined automatically from the file's header.
Waveforms can have multiple channels.
This option extracts a single channel for progcessing and discards the rest.