I actually went to Bethany's in May of 2015, but it was one of the most memorable and vivid experiences of my time in Amsterdam.
At the time, Bethany's held free jazz shows every Wednesday night, with only the drink money to keep the shows going -- a real community effort. The musicians were veteran players, you could tell; they easily swapped arrangements, played solos, and accompanied people they had only just met with skill and soul. It was a very unique format.
I was staying at Shelter hostel across the alley, and one guy from out of town who was also staying there got invited up to play guitar for a couple songs, just impromptu.
I don't know if they're still doing it or if they've perhaps moved the initiative somewhere else, but attending this special evening made me feel like I lived there.