MIDI files

Windows 7, Audacity ver. 2.0.6. *.exe
I have two MIDI files of a song. One file is keyboard solo, using track 4. The other file is accompliment, using tracks 2 for bass, and track 6 for percussion. I want to combine these two files into one stereo MIDI file so I can play it on my personal keyboard. Can the Audacity program do this?

No.

MIDI isn’t sound. MIDI is machine control for your instruments. If you use an interpreter or sequencer to turn MIDI instructions into sound, then yes, Audacity can capture the sound and mix to whatever you want—and Export to a sound file, not another MIDI file.

Koz

Audacity is primarily an audio program, not MIDI. Audacity can import, display and export MIDI files, but it can’t record or play them,
You’d really be better to use a MIDI program. See here for a list of programs that may suit the job better: https://en.wikipedia.org/wiki/Comparison_of_MIDI_editors_and_sequencers