Through the years I've learned a lot of skills out shear necessity. One of these skills was learning to read a piano roll of midi. There is more information on the piano roll than there would be in just a chart of music notation.
For example when you print a chart from a midi file the timing nuances quantize to the nearest eighth, sixteenth of thirty-second note, removing the anticipation or lag that the composer played into the midi file you are replacing.
Also notated thoroughly in a piano roll as opposed to standard notation are the dynamics. In the case of the Logic piano roll the colors are your clue here. The spectrum from purple to blue to green to yellow to orange to red is similar to ppp, p, mp, mf, f, fff. You can pretty clearly see the dynamics just a glance. It's actually easier for me to read these dynamic markings than some random p's and f's below the notes I'm trying to read.
Since the advent of samples a composer has a growing number of options for articulations. Notice the chart below. In bar 10 through 13 there are octave D's. But that's not what the composer wanted. This is the chart created from the midi file. Each note is a different sample of an acoustic guitar. In the case of bars 10-13 the low D is a down strummed open D chord and the high D is an up strummed open D chord. Knowing that now look at those four bars. See, a very simple basic folk strumming groove.
Ah, but I know what you are thinking, "why are the B notes up an octave in bar 14?". Good question. The octave, in this guitar sample, determines the tonality. If the B's were in the same octaves as the D's then they would be major chords, but what is needed here is a B minor chord strummed. Therefor the octave change. The higher octaves are minor chords. Cool huh? The chords in this cue are D, Bm, G, Em and A. All common chords in the key of D