We have a graphic of MIDI velocities of the same piece, played on three different instruments. I tried to obtain the same acoustical results, adapting my playing to the characteristics of the pianos. As you can see above, the result is puzzling. The graphic refers to three pianos, a Yamaha PF85, an good stage digital piano, a much cheaper keyboard (Roland), and in middle the fabulous Bösendorfer 290 SE, the rarest and most expensive piano in the world (therefore theoretical, at least for the most of us...).
    In order to visually emphasize the different velocity responses, I took out the MIDI velocity range of the melody notes and the MIDI velocity range of the accompaniment notes. You can see how little velocity difference there is between the two musical lines for the Yamaha and the keyboard, while the theoretical piano has much more velocity difference. This means that the dynamics of the two digital instruments are are not linear, but more compressed as they should be. Naturally their internal sound generators compensate these different responses to velocity, but what happens if we try to use the same midi output with different sounds?

F. Busoni , 512 Kb, mp3

    Quite disappointing, isn't it? A classical piano piece could be statistically not representative of the music mostly played by digital piano users, but classical music often shows better (In My Humble Opinion) where problems are .

Now, how can we make our piano midi files sound good?

    A way could be manipulate the midi values through a sequencer. Cubase and expecially Logic, for example, have some useful mathematical functions to manipulate (expand, add, etc.) the numerical midi values. It is quite difficult, though, to find the right values and it is very time-consumpting. The easiest and most intuitive way consists of manipulating the velocity response of the piano soundbank. The key to obtain the best settings usually lies in the Velocity control button/slider in the soundbank editor .

    The Slope setting determines the level of response to velocity. In this case, if set to 1.00, the soundbank will react to the velocities of the midi file exactly as they are. If set to 1.50, like in the image above, it will expand the response to the velocities by 50%: this means that the dynamics of your midi files will be much increased, compensating the mechanical flatness of the keyboard (or of the playing...). If the levels are too loud, like applying a 1.50 Slope to a midi file recorded with a PF85, where values are already very high, you can adjust them retouching the Velocity value. This value is added to the velocity treated with the slope. In case of the PF85 we will need a negative value (-32 works well) in order to reduce, for the Roland a positive value (+16, for example). Trimming these two values is easy, intuitive and, over all, fast! Remeber to activate the Velocity and Slope mostly pressing the button close to them, and check some Multiedit (or similar) button before you experiment around, or your changes will affect only one sample! (A piano soundbank has tipically many of them: the Realistic Piano as more than 20 stereo samples). In Vienna, the soundfont editor, similar parameters are even easier to trim and test in realtime.

Now a word about legato playing... (coming really soon!)