USB MIDI v1_0.pdf"Universal Serial Bus Device Class Definition for MIDI Devices"
The Univeral Serial Bus (USB) is well suited for connecting MIDI Interfaces and MIDI instruments to computers. MIDI is a recognized protocol for music control that is serving the marketplace very well. The USB builds on the strengths of MIDI by adding higher speed of transfer and increased MIDI channels through its multiple "virtual" cable support.
USB MIDI v1_0.pdf