Dedicated circuit

I’m not @jea48, but until he chimes in, I can tell you that I run a compressor as part of my hi-fi system-- fairly substantial, at one point a 1 hp 13 gallon unit- but even with smaller units, there was a nasty electrical snap that could be heard through the system when the thing cycled. The way I resolved that at the time was to run it from a 240 line with a step down transformer.
When I moved, I had more flexibility and installed a dedicated line just for the compressor that went nowhere near the subsystem feeding the hi-fi. The hi-fi has it’s own iso tranformer (10kVa- a beast) that runs to a sub panel that feeds 10 gauge Romex to the outlets. The compressor is not coming off that big iso transformer but comes from the main panel for the house and has a smaller iso transformer as a buffer.
You are probably creating a little bit of racket in a hot rod shop, but it’s worth checking to see how much noise you hear through the system when things are quiet. That "snap" was quite pronounced for listening purposes in a quiet, dedicated room. Dunno if that helps. Love to hear about the hot rods though!

I think you should run the audio from the main panel. The subpanel has the compressor and power tools which can add noise and affect current draw.
On the main panel use a 20A breaker wired to the opposite leg of appliances and the subpanel (even though the sub uses a dual breaker).
Let's see what jea48 says.

What size breaker does the subpanel use?

What size breaker does the subpanel use?
50amp  6ga wire
I agree. I will run from main panel

@OP,
I see you also have fluorescent lighting.
I think that as well as the compressor will be another reason to put a separate line to the stereo.
I would like to run a subpanel from my mains, but, due to living in a 100 year old home, there isn't space to add one. Even enlarging the panel has problems.
B