Hey there,
I'm using chops to import music into my HIP
I'm able to play the music in the background with the timeline

but whenever I'm creating a Flipbook, I'm unable to hear the sound
Flipbook only allows files to be used as a background sound

Is there any way I can set my CHOP network as my flipbook sound automatically?

is there a way for chops to save an mp3 file? maybe then I'll be able to automatically cache and read it.

You can write chops to a .wav file using ROP Channel Output CHOP node, and then play that .wav as an audio file.
List of supported chop formats: https://www.sidefx.com/docs/houdini/io/formats/channel_formats.html [www.sidefx.com]

Also I would give a try using `op:/path/to/your/chop` syntax in the Audio Filename field.
Though I doubt that it will work, since mplay (the flipbook player) is a separate process from Houdini, so most likely it won't be aware of any nodes there.
Especially since the same mplay process can be used by multiple different Houdini processes simultaneously.