In a Youtube comment there's this personal story:
I was going to Berklee back in the early 70's and I get a dear John over the phone. Thought about ending it but went down to the Jazz Workshop and there was Bill playing this Ballad. I went right up front and sat and cried my eyes out.
[sic]
I wonder whether "ending it" means
- "not going to the workshop", i.e. a forward reference
- or perhaps even "ending my life", because of the separation of his relationship