Number: 0 (coarse) 32 (fine)
Some MIDI devices have more than 128 Programs (ie, Patches, Instruments, Preset, etc). MIDI Program Change messages only support switching between 128 programs. So, Bank Select Controller (sometimes called Bank Switch) is sometimes used to allow switching between groups of 128 programs. For example, let's say that a device has 512 Programs. It may divide these into 4 banks of 128 programs apiece. So, if you want program #129, that would actually be the first program within the second bank. You would send a Bank Select Controller to switch to the second bank (ie, the first bank is #0), and then follow with a Program Change to select the first Program in this bank. If a MultiTimbral device, then each Part usually can be set to its own Bank/Program.
On MultiTimbral devices that have a Drum Part, the Bank Select is sometimes used to switch between "Drum Kits".
NOTE: When a Bank Select is received, the MIDI module doesn't actually change to a patch in the new bank. Rather, the Bank Select value is simply stored by the MIDI module without changing the current patch. Whenever a subsequent Program Change is received, the stored Bank Select is then utilized to switch to the specified patch in the new bank. For this reason, Bank Select must be sent before a Program Change, when you desire changing to a patch in a different bank. (Of course, if you simply wish to change to another patch in the same bank, there is no need to send a Bank Select first).
14-bit coarse/fine resolution. 0x0000 to 0x3FFF.
NOTE: Most devices use the Coarse adjust (#0) alone to switch banks since most devices don't have more than 128 banks (of 128 Patches each).