add function to negate Delta Sequences. (1, 2, 3) => (-1, -2, -3)
add function to traverse a Note Sequence by way of a Delta Sequence
fix inaccuracy in RhythmicDeltaSequence constuctor require
add first Hanon exercise
add public method on Scale class to get a set of notes over a given range which are in the Scale
refactor Hanon1 to general purpose for generating first set of Hanon exercises
add Hanon3 to Hanon5
add Key types to designate collections of pitch classes
add Hanon 6 - 13
Scale.toKey: name the key after the pitch class (note % 12) instead of the note
add the rest of Hanon part 1