Hello Nancy! Good question! Practicing scales is a great warm-up and technical workout.
It can be done on many different levels and speeds depending on what you want to achieve at this time.
If your goal is to learn the scale patterns to be able to read music better, it's best to stay at a slower speed while focusing on fingering and the patterns of black and white keys (topography).
This will help you when figuring out fingering, key signature, and the composition of a piece. Focus: Slow and by heart.
If your goal is to build up flexibility and speed as a technical challenge, I would work on one scale at a time until mastered. Mastered meaning as fast as YOU can fluently and with ease.
Focus: Work with different groupings and rhythmic patterns as you gradually build up speed to as a challenging tempo as you can.
Then take the speed down a notch before you continue with your next scale. This will ensure that you'll play more relaxed, and this will stay in your muscle memory until you get back to the same scale again at a later time.
TIP: It's a good idea to combine the study of scales with Hanon exercises. Pick one of the first exercises by Hanon, and practice it on the same scale as the one you're working on.
It will exercise your fingers as well as making you more secure about the scale itself!
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