Support for the SMC-Mixer and SMK-25 II piano keyboard have been merged into @mixxx and will be available out-of-the-box in version 2.5.1! Thanks to M-Vave for sending me these; I'm glad I could help! I enjoy writing plugins for DJ setups, if you have an extra controller that you want supported, or are a company that makes MIDI or HID controllers and you want to send one my way, I'm always happy to write a mapping and help get it supported in the best DJ software out there!
