I tell a lot of my students that playing fingers 1, 2, and 3 is easy stuff; we’re used to using them in our daily life off of the piano. Fingers 4 and 5, meanwhile, can be a bit trickier to master and control. Plus, when you compare the size of your 4th and 5th fingers to the size of your thumb, how can you expect the puny fingers to put in as much (or more sound)? It’s times like these when we need to really hone in on each finger and try to make each of them equal In sound. This is why I typically prescribe Hanon exercises to a lot of my students; they were written to isolate strength in each finger. This especially comes into play when you’re trying to voice a lyrical Romantic melody with the 4th and 5th fingers in the right hand (such as Chopin).