Interleaved practice feels worse and works better

Why the bar I nailed ten times in a row kept falling apart.

For years my practice looked like this. Take the hard bar. Play it ten times. Play it ten more times. Move to the next hard bar. By the end of the session it sounded clean and I felt great.

Then I would sit down to play the piece for someone and the hard bar fell apart. Every time. Same bar I had nailed the day before.

Turns out I was doing block practice, and it was lying to me.

Block practice vs interleaved practice

Block practice is repeating one thing over and over before moving on. Passage A ten times, then passage B ten times, then passage C.

Interleaved practice is mixing them. A, then C, then B, then A again. You never stay on the same thing long enough to get comfy.

Same passages. Same total time. Very different result.

Why block practice feels so good

When you repeat a passage ten times in a row, the tenth one is easy. Not because you learned it. Because the ninth one was three seconds ago. Everything is still loaded in your head: the fingering, the hand position, the sound you are going for. You are basically copying yourself.

So your brain is not really working on the last few reps. It feels smooth, you feel progress, and you stop.

The problem is that a performance never looks like rep number ten. A performance is rep number one. You play that passage once, cold, with the rest of the piece around it, and there is no second try.

Why interleaved practice feels so bad

When you switch between passages, each time you come back to A you have to rebuild it. Where was my hand? Which finger on that F? How fast was it? That little moment of searching is annoying. You make more mistakes. The session feels messy and you finish with the impression you did not progress.

But that search is exactly the thing you need on stage. Every switch forces your brain to pull the passage back out of memory, and pulling it out is what makes it stick. Researchers call this the contextual interference effect. It showed up in motor learning studies back in 1979 (Shea and Morgan), and it has been found again and again since, music included.

The short version: block practice is easier during practice and harder in performance. Interleaved practice is harder during practice and easier in performance. You pick where you want the difficulty to be.

Block practice still has a job

I am not saying never repeat things. When a passage is brand new and you do not even know the notes yet, repeating it a few times in a row is fine. You need a rough version before there is anything to mix.

The mistake is staying there. As soon as you can play the passage slowly without stopping, move it into the rotation.

How I do it now

1. Pick three to five passages. Different pieces is fine, even better.
2. Play one of them once, like a performance. No stopping, no fixing.
3. If it went wrong, fix the problem for a couple of minutes. Then leave it.
4. Switch to another passage. Every three to five minutes, something else.
5. Come back to the first one later. Play it once again, cold.

The order should not be predictable. If you always go A, B, C, your brain learns the sequence and you are back to cheating. I roll a die or let the app pick.

What changed for me

My sessions feel worse. Honestly. I miss more notes while practicing than I used to.

But the first time I play a piece for someone, it holds. And I can start from the middle of a piece without having to warm up from bar one, which I could never do before.

If your practice feels too smooth, it is probably not doing much. Mix it up.