he no longer recognized his family but could still play and sing well
The above quote reveals a mystery .. musicians use a different part of their brain to tie things together, apparently.
I know many studies show musicians learn differently (and as a result are usually 'smarter' when tested). The fact that the music still made sense to him when other familiar things didn't says something, and hopefully contributed to his quality of life at the end.
He will be missed.
/I've been a fan of Glen for years so a pretty sad event for me. And anyone else he touched.