[ytturbed]

>When she does this with students, she asks them afterwards, “Was anything fuzzy?” It’s usually the part that they were messing up that’s fuzzy.

This is genius. Reminds me of the rule that if something feels fuzzy at the instrument it's always a conceptual error about the piece rather than poor coordination or poor finger strength.

>Why is it better to practice every day for an hour, instead of seven hours on one day of the week?

For the same reason that it's better to practice for 10 minutes several times per day instead of one hour straight.

[vshan]

Not the same reason, as it is better to practice one hour every day of the week instead of seven hours on one day because of the sleep you have.

[ytturbed]

Sleep is a given. The brain is learning continuously, not just during sleep. Go back to a section of a piece after 15 minutes doing something else and notice it has become easier.

[cheepin]

Sometimes it's even easier after just 1 minute away. I code and play music, and I've made a habit of occasionally walking around the house, petting the dog, then back to where I'm working/practicing. It doesn't take long, but it works strangely well.

[ytturbed]

Yes. There's something about walking isn't there? Returning attention back to the body and the senses amounts to relaxing after hard concentration. Perhaps petting the dog enhances that, the body being where emotions are felt. Scientists seem to suspect that walking or just standing occasionally is important for health.

To complete the argument about learning: you play the tough section, correcting a few errors. Then you go away for a bit, and during that period the brain updates its hardware to include those corrections. The mistake is to hammer/saw away repeatedly and interfere with what you have already achieved, wasting time and effort. I think the OP kinda acknowledged this by recommending switching at whim between different tasks within a practice session.