In this chapter, you learned a great deal about audio under Linux in general and about the ALSA sound system in particular. You know how to configure and test the audio output of the Raspberry Pi board itself and how to set up your USB audio gadgets for recording.

You learned how to use SoX to record sound and store it in multiple formats, how you can avoid typing the same thing over and over with aliases, and how to keep a recording session running with tmux even when network connectivity is spotty.

Armed with only SoX and SSH software, we turned our Pi into a very capable radio—we can put it in a room and listen in, like a baby monitor, or we can let it broadcast our voice and music to the world.

You also learned how to apply SoX effects to spice up your voice or let the Pi make the noise using eSpeak. Then we looked at a few different techniques to control the timing of our sound-related mischief including noise detection.

Finally, we set up our very own phone network using SIP Witch...