It can be a gig or an album. It could be an event or a musician's own lightbulb moment.
Mine has to be the day in 1986 when I visited John Coltrane's house in Philadelphia and listened to his cousin Mary talk about living there with him, listening to him play.
I felt closer to one of my jazz heroes than ever.
A couple of years later I sat on the front row at the Barbican and heard Gerry Mulligan play. That definitely gets to moment number two.