It happens a lot. You know, a fabulous melody in the right hand to be played in octaves. Maybe with interesting things happening in the middle or maybe not, but we’re not considering those at this moment.
What constantly amazes me is students (not to mention virtuosi) who automatically and for no good reason give all the weight to the top, with the thumb just kind of tagging along in support. But give the lion’s share of weight to the thumb with the little pinkie just adding ‘harmonics’ and you might be astonished at the difference in the character of the passage, not to mention the intensity of the music.
It makes good logical sense when you think about. Obviously (or, it seems, maybe not!) the shorter treble strings have far less potential to sing out our glorious melody than the middle register. Which, as an aside, is why so many truly glorious melodies in Schumann and Brahms are found in the tenor region of the instrument.
Anyway back to our octave melody. Playing with the main weight on the thumb can give you and your audience a surprisingly different, and often most welcome, perspective on the music. But choosing between pinkie or thumb are not the only options. How about giving thumb and pinkie exactly equal weight? – think Tchaikovsky, with soaring melody in first and second violins.
It works with left hand octaves too. More weight on the thumb here is a good counterbalance to the disproportionate heaviness of those long copper-coated bass strings. Next time you see an orchestra count how many cellos there are compared to double basses. Now what does that tell you?
Sometimes you might have a ‘dramatic moment’ when you have to play four bare octave A’s (or whatever) all together, fortissimo, with both hands. Put the maximum weight here or there, or in various combinations – by my count there are at least 15 possibilities – and each one gives a quite different sense to the musical moment/drama.
So let’s hear it for the thumb. Far and away the most musical digit we have.