ArpMelodyMachine

[afternoon]

Implement the ArpMelodyMachine, which should generate arpeggios.

• Params: root note, chord type, contour.
• Sequence should be the correct length, but arpeggio will repeat or truncate if length is not equal to the number of notes in the arp.
• Contours might be simple up, down, etc, as in typical arpeggiators, but also may be more complex, or even stochastic.