Footsteps - The notes at the beginning are so isolated. This is music that will loop in the background while you play, so I feel like it would be better to even things out instead of having such a distinct beginning and end.
Plan, What Plan - This one's good: very Marathonesque, and possibly my favorite so far.
Frog Blaster - The piano sounds better in the classic version, surprisingly - it's just too low a register to sound good in the other version.
See You Starside - In the MIDI version, I much prefer the piano over the instrument that plays the melody before the piano repeats it. I like the rhythm once it gets going, but the start & end feel barren going to a solo the way they do, similar to other songs like Footsteps.
Durandal Theme - You definitely got that echoey rock anthem sound. I miss the breathy vocals saying "Marathon", though.
Flippant - Funky! In the middle section, the notes get buried under the sustained sounds. And as a personal preference, I like the soprano line in the last third better when they sound more like singing, over the more purely synthesized sound you have.
You know your stuff when it comes to composition. It beats the stuff I've cobbled together in GarageBand, in any case
. Even the song titles are thoughtfully chosen. Good music deserve a good title, as much as a good level does.
Listening to these gets me thinking about more dynamic music. Parts of this are good for reading a terminal, and other parts are good for blasting Pfhor. It'd be cool if a scenario changed the music accordingly.