I easily enter this state with music, I would imagine everyone finds this quite easy while watching particularly good TV, a film, an absorbing book, etc. This isn't meditating IMO. I also meditate from time to time... this is a completely different state of awareness. The point is to increase awareness and mindfulness. Absorbing oneself in a piece of music is to shut down awareness of everything else. This is not enlightening or helpful to most people. The ego will be happy though in the illusion of meditating without the usual 'monkey mind' chatter. It can also be relaxing. But it is not a useful tool for increasing awareness and mindfullness.
I think we're talking about different things. Becoming absorbed in a piece of music is something different, to me, to focusing your awareness on the sensation of listening. The former is quite passive compared to the latter and with the latter you get all the usual "monkey mind" chatter that you get with breathing and bodily meditations. There's an exercise where you focus your awareness on the music and on your breathing at the same time and try to hold that awareness. This is the kind of awareness I'm talking about, rather than that of merely getting absorbed in a piece of music. Otherwise I'd be calling headbanging at a heavy metal concert meditation.
If I've been explaining myself poorly up til now I apologise, my concentration has been abysmal for a few weeks.