Musical is mostly rhythm and pace (and timing). A technical term that takes a lot of time to become sensitive to detect it directly… took me decades. A way I detect it is , does my foot just naturally want to start tapping to the music. It isn’t about details, it is about how captivating the music is. Typically analytical system can be devoid of it.
As an example when my system was spectacularly detailed I would listen to an album with interest… but never more than 30 - 40 minutes. Now my system is incredibly musical and I have a hard time tearing myself away from it after a couple hours. I listen three hours a day… and would listen more if I had time.
To me, the best way for an audiophile to loose his way is to become enamored with details and slam and find his system devoid of musicality. Tubed components tend to be very musical.