That's what it is that you rehearse - the making of music, not the playing of notes as abstractions.
“If the past has been an obstacle and a burden, knowledge of the past is the safest and the surest emancipation.”
“Trust your gut instinct over spreadsheets. There are too many variables in the real world that you simply can't put into a spreadsheet. Spreadsheets spit out results from your inexact assumptions and give you a false sense of security. In most cases, your heart and gut are still your best guide.”