> If the passage is only ten seconds long, you can practice it twelve times in just two minutes, which is 30 times more efficient. Your example timing makes me

> If the passage is only ten seconds long, you can practice it twelve times in just two minutes, which is 30 times more efficient. Your example timing makes me suspicious that this is a theory you haven't actually tried to put into practice yet. Ten seconds is an eternity for a drill of a difficult passage. For an amateur, that's almost guaranteed to be too much music for them to isolate the difficulty. That means instead of a success rate of 100% on the drill they'll get something considerably less. For an amateur, "difficulty" usually means they were already playing it wrong before they began drilling it. So any mistakes in the drill help reinforce the initial muscle memory for that passage. That makes it extremely likely that they'll repeat the same mistake when you add an audience and nerves. Drilling passages that are too long does at least decrease the chance of the player losing their place-- they have practiced starting at various spots that aren't simply the beginning. But they are only "30 times more efficient" at playing the piece with an unnecessarily high error rate.