[FFmpeg-user] toggle between two audio streams

[Jon Beyer]

I'd like to be able to replace the audio with constant tones for certain
intervals of a video.  As an example, I might have a thirty second video,
and want to insert 440 Hz from 5 seconds to 10 seconds and again from 15 to
20 seconds.  Assume that I already have the 440 Hz tone in a .wav file that
is five seconds long.  Is there a way to specify a filter that toggles
between the video's audio stream and the .wav file over the specified
intervals (i.e. 5-10s and 15-20s)?

Thanks in advance!

Cheers,
Jon