The more detail the better.
Planning rehearsals sometimes feels like my arch nemesis as a conductor. I like the flexibility to follow challenges and react in the moment to the needs of my students; I also don’t often have the mental bandwidth to reliably sit quietly and prepare for rehearsal.
But I love it when I do have a detailed, specific, goal oriented plan for rehearsals. It’s for two reasons.
The less important reason is that I can be more targeted and efficient in leading the rehearsal.
The more important reason is that I can better assess failures – my own and the ensembles. With specific rehearsal plans and benchmarks, I can really see where I drop the ball, where I can focus more attention, and where the ensemble is struggling more than I expected.