Universal Serial Bus Device Class Definition for MIDI Devices

1 Introduction
Following is the USB Audio Device Class Definition for MIDI Devices. It is designed to cover the widest range of possible MIDI applications and products. This document must be considered an integral part of the USB Audio Device Class Definition.
1.1 Background
MIDI, introduced in 1983, is a mature standard with many existing products and applications. It is a standard that defines not only the data protocol for exchange of musical control information but also the hardware connection, used to physically exchange the data. Therefore, transferring MIDI data over another hardware
connection like USB is not really conforming to the MIDI specification and will be called USB-MIDI from here on.
1.2 Purpose
This specification for MIDI exchange over USB is designed to be an elegant method to enable a wide range of MIDI system configurations, from the simplest to the most complex. Furthermore, this specification expands on MIDI, allowing applications not possible with non-USB MIDI configurations.The first two figures show simple USB-MIDI systems that form the base of any MIDI related system on USB and the third example shows a very complex USB-MIDI system combining variations of the first two. Figure 1 shows a simple USB-MIDI interface, which would allow many existing non-USB MIDI devices to connect to USB.