There are 3 sets per night.
I recommend you reserve if you're going to the 1st set.
They don't take reservations for the 2nd or 3rd set because people are not obligated to leave after the first set. You can stay all night if you want to. So, to be safe, I recommend reservations.
We went there as part of the Montreal Jazz Festival to see a well known pianist, so yes, reservations were a must that night. We went early and got a really good table, had dinner first. It was fabulous. The concert I mean. The food was fine.
We didn't have rezzos but were there early and were OK. The consensus seems to be that you should reserve.
I recommend reservations. We had them and would have not been able to be seated otherwise.
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