What codec would you use to make the smallest possible audio file? I'm talking in the range of a few kbps. Audio quality is irrelevant as long as it is intelligible.
Perhaps whatever compression phone companies use?
>>60002767
mp3
https://en.wikipedia.org/wiki/Speech_coding
Opus?
>>60003212
2nd for opus.
See here http://opus-codec.org/comparison/
>>60002767
AMR maybe? Like what we used to have on dumbphones
>>60002767
Midi.