FreeMIDI

FreeMIDI is a virtual studio management application by Mark of the Unicorn (MOTU) for the Classic Mac OS. It is used to mimic the physical setup of MIDI devices that are connected to the computer and provide applications and the Mac OS a way for referencing them.

OMS by Opcode also performed similar duties. Some MIDI interfaces provided drivers for both FreeMIDI and OMS, while some only included drivers for one or the other. FreeMIDI included an "OMS Compatibility Mode" which allowed FreeMIDI to communicate with devices in OMS.

Under Mac OS X, neither FreeMIDI or OMS are used, as those duties are covered by OS X's included Audio MIDI Setup utility. Interestingly enough, many of the concepts of FreeMIDI (such as the mimic of the physical MIDI setup in the user interface) were borrowed and integrated into OS X.