We would like to share audio files with remote users, without them being able to download the file. Is there a way of doing this without combining nextcloud with something like subsonic?
Short awenser: no.
Longer awnser: What might be possible is to make it hard for people. But this comes always down to some form of obfuscation I think. In the end if they can get the bits of audio they can save those. Heck, if they really want the audio they can of course just record the audio that is playing.