Hello rnd_j and welcome in uos forum.
> I think there's a bug on uos_flat (or a mismatch between it and the SimpleRecorder example). Ooops, indeed the default AudioFormat was not defined in AddIntoMemoryStream() of uos.pas.

It was just fixed with last commit of
https://github.com/fredvs/uos/Thanks to note it.
Fre;D