So, how does one make the hammer hit the string more beautifully? More richly?
pizno, try this:
sit at the piano (you're going to use your left hand)
stiffen your arm (very important!), in fact stiffen your hand, and even your fingers, and punch out a 'c' octave, and hold it down. do it again. absolutely as hard as you possibly can.
then once you've done that, scroll down.
this time, take the same hand, and let your elbow relax, your wrist relax, and your fingers not half as stiff. hold your arm at a right angle (away from the piano) and let it drop down. do it over and over again, not using muscle, just let the natural weight of the arm carry it down.
then try this at the piano. instead of stiffening everything like before, let your hand drop down using arm weight, and let your elbow absorb some of the blow, like a shock absorber. keep your wrist relaxed and let it come down slightly farther than the hand does. now don't use a wimpy sound, don't do it softly or anything. get a big sound, drop those fingers into the keyboard and hold them there. if you can't get a big sound, then use more arm weight. let the entire weight of your body behind the arm come dropping down into the keyboard. i can actually get more sound this way then if i stiffen and use my arm muscles.
now see if there isn't a difference between sound. when you stiffen everything and punch out an octave, you get a harsher sound. this applies to chords, single notes, arpeggios, everything in fact. that's one of the things that makes an artist different from another artist.
there's also the entire phrasing aspect to tone, using tiny and unnoticeable crescendos, decrescendos, and accents to compliment tone. but i think i've gone on long enough about arm weight, so someone else can weigh in on phrasing.
hope this helped.
w.e.