It’s interesting, comparing performance when I am singing and playing guitar to when I’m singing with others accompanying.
When I am singing and playing there is, quite frankly, more to keep track of. The mind stays busy because I not only need to keep track of the lyrics (or, at least, of my mental map of the lyrics,) but of the map of the chords/chord structure, and have some awareness of what my fingers are doing on the guitar.
Just singing…is so easy, it feels effortless. I am still aware of the harmonic structure – but not as chord names or tonic/dominant, etc., only as a sound map of what is supposed to be going on around me.
And, actually, my training as a soloist singer was very germane to yesterday’s performance of Blowin’ in the Wind. Why? Because there was very little rehearsal. Very often the chords being played were different from what I play when I play Blowin’ In the Wind on guitar. I had no idea what the tuba and fiddle were going to be doing. So, in the absence of any plan – and between my voice, the lyrics, and the microphone my voice was the most attention grabbing musical instrument in the mix – I simply determined that I would “forge ahead” and lead out and that the rest of the musicians would follow my lead or be damned. Quite often a little voice in my mind would mildly declare that “the current harmony is not what was expected” and that realization was shushed by another authoritative voice that figured “it will all work its way out – just enjoy the experience” – something that I first realized when I was about 10 years old and my father completely botched the piano accompaniment for my solo in church.
I have a friend who plays in Latin bars, singing Spanish songs and playing guitar. I recently found out that he has had backing tracks (rhythm tracks, maybe more than just rhythm tracks,) created for his songs so that he can play against a “recorded band” rather than a live band, because he doesn’t like it when live (unrehearsed) band does unexpected stuff when he is performing. It’s interesting how strong a drive there is to control an experience. In this case, the desire for control leads him to enslave his live performance to a recorded track – yet this is preferable for him to the unknowns of live performance with unknown entities.