ABSTRACT
MIDI (an acronym for Musical Instrument Digital Interface) is a digital control system developed to enable synthesizers, keyboards, sequencers, home computers, drum machines etc., to be interconnected via a standard interface. This standard specifies both the type of connector and data signal protocol and level. At its most basic level MIDI is a means of setting one instrument as slave to another. At its most sophisticated it can be used to create, store and replay complex musical compositions, and can be used to control ancillary equipment such as mixers and effects units. All communication in MIDI is carried in multi-byte serial 'messages'. The system is asynchronous, the data only being transmitted as required. Binary 0 is represented by a current flowing in the link, and binary 1 by no current flow. Each byte is preceded by a start bit and followed by an end bit. The data rate is 31.25 kBaud, ± 1%. This gives a duration of 320 μs for each 10-bit message. In the discussion that follows, the presence of these start and end bits will be assumed, and attention will be concentrated on the message bits. For most message types, the first byte of each message is a status byte, called the 'header', indicating the nature of the following data. As Figure 6.1 shows, these messages are of two broad types: channel and system.
