Thanks much for getting back to me.
I entered amidi -l into the console and got this response
Dir Device Name
IO hw:0,0 f_midi
I then entered dmesg -w, then plugged in the Yamaha P-115 into the USB slot. There was no activity, so I guess that suggests that the Yamaha is sending a message that the Raspberry Pi doesn’t understand. If it would be helpful I could post everything returned by the dmesg output, but if the essential question is whether there is any activity registered when the keyboard USB is plugged in, the answer is no.
I have installed Zynthian from the 2021-03-25-zynthianos-stable-2103.img image and configured it per the very helpful instructions provided in Beginners Headless Zynthian Tutorial - ZynthianWiki. I ran the software update after installing and have ran it again for good measure. I also ran sudo apt update and sudo apt upgrade.
Please let me know if you have any other suggestions. Thanks again for your help!
Regards,
TK
UPDATE: I forgot to mention earlier that I have successfully used the Yamaha P-115 to send MIDI to my Windows computer, so I know that it sends MIDI, just don’t know whether it sends MIDI in a format that the Raspberry Pi will recognize.