I noticed freepascal has some PortAudio related code (AFAICT fredvs has contributed some units here too)..

Can portaudio, the cross platform API, be used on macOS?

Does it allow writing audio files and adding data to existing audio files?

Looking to cut/paste audio into an existing audio stream... And also add "silence" to the audio file (dead air, or breaks between audio.. blank audio state).

This can all be done on MS Windows likely using MMSystem, but would be nice to write audio in a cross platform way.

Also noticed there is FPSound, but it is for reading audio only, so far.