For each track in your collection there's an ideal volume. A sweet spot in level where the system shines and the music is perfect.
That sweet spot varies across systems, rooms, tracks, and the number of people listening.
How to nail that setting? With a little help it's not hard.
The good news is that most of us can instinctively dial in the right loudness if we have a few tips as to what we're listening for.
Here's a short guide:
Image Size: The volume affects the perceived size of instruments or vocals. Too loud, and things feel unnaturally enlarged. Too quiet, and the entire soundscape contracts (though interestingly enough, individual elements maintain their relative proportions until the volume drops to near-background levels).
Blaring or barking: A glaring sign you've gone too loud.
Presence: If a song seems lost in the room's ambient noise, it's likely not loud enough.
You'll have to find your system's baseline and then tweak it based on the song and the number of people listening (which is more often than not an audience of one).
I recommend starting with a known good track. If you have any of the Octave Records setup discs, that's a great place to start.
Sometimes, just knowing there's a correct level for each and every track can make a huge difference in your forward progress.