Remembering scale fingering without quite understanding why it is we do what we do can be hard. I'm going to provide you with a method of understanding and working out fingering with a tip on when to use finger 4 for 2 octave scales that I hope will help.
There are basically three finger patterns used to play scales. Pattern One is used as we go clockwise down the circle of fifths, from the key of C to the key of E. It is used for the relative minor of each of these keys as well, except for B minor. Pattern Two is used for F Major, B Major, and B minor. And Pattern Three is used for as we go anti-clockwise down the circle of fifths for the flat keys: Bb, Eb, etc.
We're going to discuss Pattern One in this post, and we'll look at Pattern Two next week and Pattern Three the week after.
Pattern One allows our hands to remain in a natural 5-finger position on the keyboard. Let's look at the R.H. first. Our goal for the R.H. is to start with the thumb on Do and then end with the pinky on high Do. In order to this, we use fingers 1 through 3 for the first three notes, Do, Re, Mi. Then for Fa, the thumb crosses under the Finger 3, so that our hand falls into a natural five-finger position that takes us all the way to high Do.
When you get to Ti, and you use your fourth finger on Ti, you have a choice. If you decide to play a one-octave scale, you'll use the pinky on high Do. But if you want to continue to play another octave of the scale, you bring your thumb on to high Do.
When you play the scale descending, your goal for the R.H. is the same: to play high Do with your pinky and to end on Do with your thumb. In order to do this, you do the exact reverse of what you did going up. So, you play Do, Ti, La, Sol, Fa in the five-finger position your hand is already in. Finger 3 then crosses over the thumb to play Mi, which allows you to use your thumb on Do.
Now, if you want to continue down another octave, all you have to do is bring your fourth finger back on Ti, just as you would have if you'd used your pinky on Do instead of your thumb.
All you have to remember for two-octave scales with this method is that Finger 4 of the R.H. always plays Ti.
For the L.H., we begin with our pinky on Do and we want to end with our thumb on high Do. So, we play Do, Re, Mi, Fa, Sol using the five-finger position our hands are already in. Note that finger 4 plays Re. Once you've played So, Finger 3 crosses over the thumb to play La, and you'll end with your thumb on high Do.
What do you do, if you want to continue playing another octave of the scale? Your goal is still the same, you want to end with your thumb on the next high Do. In other words, the high Do you've just played is the Do for the next octave. If you were beginning on this note, you'd have played it with your pinky and quite naturally used Finger 4 to play Re. So, that's what you'll do now. Let finger 4 cross over to play Re.
When you're coming down, once you've played La with Finger 3, let the thumb cross under to get to So. This puts you in a five-finger position that takes you to Do. However, if you wanted to continue playing another octave, after playing Re with finger 4, you'd bring your thumb and use it instead of your pinky to play Do.
So, for L.H., when you play 2-octave scales, remember that it's Finger 4 that plays Re.