ABANDONED. boy with glowing alien in cave

[Iris]

I'm trying to figure out this book - all I remember is that it was a children's book, and was about some sort of an encounter with an alien or extraterrestrial being. I think the protagonist was a boy, and he is able to communicate with the alien via telepathy. The alien is in the form of a glowing ball of light that lives underground in a cave or an underground hole or something. There is a scene where the boy goes to the cave/hole and plays the guitar for the alien. I think there might have been something along the lines of, the alien didn't understand humans so the boy was trying to educate it?
I know that's not much to go on, sorry....

[Lobstergirl, au gratin]

When did you read it?

[Iris]

About 16 years ago I think.

[Lobstergirl, au gratin]

Iris left the group. Moving to Abandoned.