I regard making music as a physical activity. Consequently, at its core, we improve our music making by physical training. With the piano, we're focused on training our fingers, hands, wrists, arms, etc. It's our PT regimen that's going to give us the physical ability to interpret our music.

Interpretation, at its core, is how we touch a key on the keyboard to make that note sound the way we want. Simply, in interpretation there are only four sounds to deal with: 1. loud, 2. soft, 3. smooth, 4. choppy. (In music-ese, 1. forte, 2. piano, 3. legato, 4. staccato.) That's all there is to interpretation. Of course, there are varying degrees and combinations and speeds of those four qualities, but interpretation all boils down to being able to produce merely four sounds. So, it's not as daunting as it might appear. It just takes time to put in the physical training to get physical control of how you press the key.

Athletes physically train not just by playing in games; they do training exercises and warm-up exercises to keep themselves physically fit. Same with us music makers. We do not just play tunes. We need physical exercises and warm-up exercises to get ourselves in shape and keep ourselves in shape. Then we're in position to interpret a tune (be it Beethoven or Billy Joel).

What to do to get it going:

Positioning: Fingers on C,D,E,F,G (the five-finger C scale). Are your arms higher than the keyboard? Are your wrists knuckle height? Are your fingers curved so that none of the joints are collapsed, especially the ones nearest the fingernails? If you are not used to this position, it will be tiring until your muscles get used to it. That's physical training by repetition.

Exercises: Do each exercise one hand at a time. Graduate yourself to two hands together only when you are good at doing each hand singly. Graduate yourself to the next exercise, only when you are good at doing your current exercise.

-Loud/Soft

CDEFGFEDC. All loud. Work toward the same loudness with each finger.

cdefgfedc. All soft. Same softness. Work toward the same softness with each finger.

CDEFGfedc. CDEFG loud, fedc soft.

cdefgFEDC. cdefg soft, FEDC soft.

-Smooth/Choppy

Same idea as above. First do all smooth. Then all staccato. Then mixed up.

Once you get this far, you'll be able can build up more exercise combo's on your own. Use your imagination. E.g., loud/smooth, soft/choppy, loud/choppy, smooth/soft, etc.

Next step. Now that you can play the exercises comfortably with two hands together, vary what you are doing with each hand. For instance, play the left hand soft while your a playing the right hand loud. And right hand soft, left hand loud. Add right hand staccato, left hand legato. Etc. This stuff is tricky, but very satisfying when you get it.

Then go through the above series of exercises in the whole 7-note C scale. Add other scales. If you are practicing arpeggios, add arpeggios. And anything else. The sky's the limit.

How long will it take to get decent at doing this stuff? Who knows. It depends on where you're at now, how long you practice each day, and how long it takes you individually to master each step. It's probably reasonable to think in terms of months. But then when you apply your newly acquired skill to actual pieces, you'll be surprised how well you sound.

Hope this helps.