Mixer: start multiple voices simultaneously

[dhalbert]

Current audioio.Mixer can only start one voice at a time. I'm not sure what the minimum lag is between voices. Ideally multiple voices that need to be synchronized could be started at once.

Example use cases:

• Multi-track musical piece, where you want to play all tracks at once, or turn some tracks on an off.
• Synthesized audio where phase differences are critical.

See #1242 (comment) for more detailed discussion (open up the third resolved conversation to see it).

[tannewt]

I think you can achieve this by calling play with the mixer after calling play on the mixer. It would look something like:

mixer.play(sample1)
# Occurs at the same playback time as sample1 because nothing is reading the mixers output
mixer.play(sample2)
audioout.play(mixer) # Starts playing the mixers output

This trick should also apply to a Mixer being played by a second mixer that is running "live". I haven't tested this though.

[dhalbert]

Closing because there's a workaround of the original problem, and we are far ahead, with MixerVoice, etc.