Channel Transformer is a utility (not only) to map MIDI Channels. It can also:
Set a fixed velocity per channel.
Set a fixed note length per channel.
Change the key (root note and scale) for all channels at once.
Transpose notes up +/- 24 semitones up or down.
Monitor and log incoming MIDI messages.

Changelog:
v1.4 – try to fix hanging notes when changing scale.
v1.5 – bugfix: Show transposition value on step knobs.