A young piano student has asked this question: "I would like to have opinions on which fingering to use in the twelfth bar work of Schubert Impromptu Op 90 no. 3 in G Flat Major. Precisely where you "beat" for the first time on those E flat and C flat together. My problem is that I just can not give the correct pressure not to make it look like a hammer."
Here the musical example:
"The question is not at all strange, it is very sensible! I'll play with the fifth finger on the E flat and fourth with the C flat supporting the weight of the arm on the fifth finger, "leaning" softly, without a hammer! You will say, easy to say! Depends on technique".
Now I add something. The word "support", not surprisingly, is used in a number of cases in instrumental technique and also in the technique of singing. What does it mean support? It means "to lean, to stand on something, something supportive": so it's the exact opposite of what you do when you make an effort, you lift a weight, it faces a struggle. In everyday life, we lean when we need to stand up to support us (and, metaphorically, we rely on a few people when we feel discouraged or distressed ...).
So, lean means countering effort with an aid which, in the case of the piano, we are given simply by the force of gravity.
But more importantly (and this is the sense of the question) is that properly leaning the weight of the arm can also change the sound between the fingers of the same hand. This is necessary when we, in cases such as that place in this example, the composer needs to play melody and accompaniment in the same hand and therefore, by implication, requires two different sounds in the same hand.
Of course, you do not get an immediate: it is an instrumental technique that acquires the appropriate exercise.