[CM] Can snd do this?

[Bill Schottstaedt]

 > What I envisage is playing the wav file through snd, pressing a key
 > (<SPACE>, say), have the playback stop and switch to record mode,
 > read into the microphone to insert, release the key and have a
 > silence of a few seconds inserted, then continue playback.

I think you could write such a function in Snd, but it sounds
tricky.  My guess is that it would be faster, and less error-prone,
to take a less high-tech approach: first record the prompts, either
as one long file or a bunch of short files, then set marks to
guide the mixing process, then do all the mixing in one step,
then (probably the longest step), clean it all up, adding silences
and so on.  By taking it one-step-at-a-time, you make it easy
to back up and try again, and you know that you're actually
making progress.