The use of the word "musical" as an adjective

Well given the responses posted here I'd say that people have a pretty clear understanding of the term "musical". When I use this term it is meant as a compliment.  It implies music reproduction that breathes life and emotion and allows engagement and a joyful spontaneous interaction. Toe tapping as 1markr wrote. I believe people know it when they hear it. 😊

Non musical presentation would on the other hand be sterile, mechanical,  dry and lacking emotional involvement.  Some would say that the music sounds "canned" or a processed. This is not a compliment. 
Charles 

Right. Natural sounding, unintimidating, involving, having substance.

I was going to try to wordsmith a response but why bother when nonoise got it pretty much right to begin with!

Perhaps PS wants something specific.

Listen to Barber's Adagio for Strings, twice, without wincing, once.

I would apply it as an adjective to speakers and components that don't exhibit distortions that distract me while I'm listening to music.