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Axiom Line User Guide
Section 5: MIDI Messages Explained
5.1 Program & Bank Changes Explained
The original GM MIDI Specification was designed to access only 128 different sounds (a lot at the time) using Program Change messages (0-127).
Later on, in order to access the expanded set of sounds used in General MIDI (GM), Bank Change messages were added to the specification.
Within each bank there are a possible 128 different sound patches that can be accessed using the standard Program Change command. Using
the expanded 14-bit Bank Change command, there are now 16,384 banks available – each with 128 sounds patches. Technically speaking, the first
7 bits of the 14-bit Bank Change message are sent in a single byte known as the Bank LSB. The last 7 bits define another byte known as the Bank
MSB. The BANK LSB is the most commonly used. This allows for 128 bank changes, and often there is no need to send a Bank MSB.
You will find almost all MIDI devices respond to Program Change commands and many are organized according to the GM listing. In all General
MIDI devices, the different sounds are always organized in the same way from device to device, so the piano sounds are in their particular place,
the string sounds are in their place, the drum sounds and so on. All GM devices (both hardware and software sound modules) are clearly labeled
as such, so you know that their sounds are organized in the General MIDI structure. So when a GM device receives a MIDI Program Change, it
calls up a type of sound that you expect from the GM sound set. All non-GM devices call up unique sounds from their memory upon receiving
MIDI Program Changes. Since the sounds in a non-GM device are not preset to a particular order, you need to take a look at the device itself to
see which sound you want and at which location in the memory that it lies. Many VST instruments such as Native Instruments' FM7 or the synth
modules in Reason are non-GM devices.
Bank Change messages are useful when calling up sounds from a large library that may exist in a particular sound module or software synth. For
example devices that are built with Roland's GS specification or Yamaha's XG specification require you to specify a Bank Change in order to access
the extra voices and effects that these devices provide.
Sending Program, Bank LSB and Bank MSB data is made simple using the Axiom. Simply press the Edit button, followed by the Program, Data LSB
or Data MSB key and enter the program or bank change you wish to send.
5.2 RPN/NRPN's Explained
Non-registered parameter numbers (NRPN's) are device specific messages that enable you to control synths and sound modules via MIDI. The
MIDI specification defines open parameter numbers to allow manufacturers to specify their own controllers. The more common of these are
registered by the MIDI Manufacturer's Association and are now part of the MIDI specification (hence the term Registered Parameter Numbers
– RPN's). (See Appendix F.)
MIDI controllers 98 and 99 represent the NRPN LSB and MSB respectively, while 100 and 101 represent the RPN LSB and MSB (see the MIDI controllers
list in Appendix D). To transmit an NRPN/RPN, these two controller messages are sent along with their user-specified values. A further controller
message and value needs to be sent to specify the (coarse or fine) value adjustment. This is specified by controller number 6 (Data entry) for coarse
adjustments or number 38 for fine adjustments.
A list of NRPN's is always given in the user's manual of any device that receives NRPN messages. It is always necessary that the NRPN MSB and
LSB be sent together. Both will be specified in the device's manual. You may find the manufacturers have specified the numbers in hexadecimal
format only. In this case, use Appendix C to translate the value to Decimal.
Your Axiom keyboard makes the process of transmitting NRPN's easy. All you need is to enter the desired NRPN LSB by pressing the LSB/Data
button twice, enter the NRPN MSB by pressing the MSB/Data button twice, and as you move the controller, the selected NRPN message is sent out.
Assign NRPN coarse to make big sweeps, or NRPN fine to make slight adjustments.
Section 5: MIDI Messages Explained
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