Thanks, volovicg, for asking your preliminary basic question. I'm using M-AUDIO Keystation 49 MK3. I realized that I must have had the advanced button inadvertently pressed and played the key that activated channel 15. Problem resolved!
My mAudio 49 won't work with Mojave and Logic X. The midi monitor shows nothing coming in. It used to work with OS 10.6.8 and Logic Studio same with my little KB-37 Toneport from Line 6. I guess I always thought USB MIDI would always work but the freeware, MIDI monitor says it don't. I'm guessing Mojave is the culprit?
From Mac OS 10.6 to 10.14 is quite a big jump. USB has certainly changed and most hardware drivers need an update.
If you go to Downloads in the Line 6 website and use the dropdown menus to search for TonePort KB37/Drivers/Mac OS X, they offer something and link to a page 10.14 driver installation change with some information about new Mac systems.
M-Audio offers a driver for Mac OS 10.14
Use the "Support/Drivers & Updates" page.