As a function added to the G-Major from software version 1.07, midi mapping allows an incoming MIDI Program Change message to be assigned to call up any of the G-Major´s internal program numbers.
For example, an incoming MIDI Program Change message with a value of 44 might be mapped to call up internal program number 95, MIDI Program number 67 might call up internal program number 14, and so on. There are a variety of reasons for using this function.
When using several Midi controllable units in a live situation, a single program change message from a controller can simultaneously call up several sounds located in different MIDI modules at different patch numbers.
On devices which have more than 128 patch locations, but don't respond to bank select messages, internal programs higher than #128 can be accessed using mapping.
The most basic reason: convenience! Rather than copying patches around to put them in the order you want or need, simply use patch mapping to establish the desired order, and call them up through MIDI.
For more information about how to set up MIDI Mapping, please refer to this FAQ.