In reply to White spaces:
>no rhythm
The Fourier transforms on blocks of text show a periodicity in text faces, bands of black and white. Another way of saying this is that in a the vertical strokes in a word tend to fall near vertical lines a set distance apart, namely half the width of the n.
As Héctor says, deviation from the exact periodicity is part of what we 'read'. It is analogous to the regular beat in music, and the varied rhythm over the beat. When the typeface doesn't have that periodicity is like a dancer who 'loses the beat,' and can't dance to the music.
One feature of good handling of white space is to get the widths of the characters and the side bearings in a font to relate to each other so there is that strong, but not totally regular periodicity. I think failing on rhythm, harmonious widths and sidebearings, is the most common failing in type design.
Because our eyes do not move continuously across the page, but in jumps, saccades, the analogy with music is not complete, but the periodicity, with regular beat and varied rhythm is analogous.
