For me, the music in the two made the games for me.
I'd first become acquainted with MM6 back in 1998; my mom had played the previous games (Swords Of Xeen, etc.) and MM6 had just come out. Even though I'd never taken an interest in the previous releases, she suggested that I give MM6 a shot, as I was heavy into Microsoft Flight Simulator. (She mentioned that it was a first-person RPG, which she likened to FS.) I got home one morning (Worked third shift) and it was my Friday, so I loaded it up and said "What the heck."
Next thing I knew, it was about ten hours later; she returned from work, and I had slain hundreds of goblins in New Sorpigal, as well as fallen in love with the soundtrack. I'd also inadvertently found a quest item that she'd been racking her brain over, so in return for showing me where to return the item, I showed her where to find it.
Three tunes from MM6 that are my favorites: the main New Sorpigal tune, and also the one called "Further Exploring the Temple Of Baa." I also liked the title track, which plays when you first open the game. (It also plays in Mire Of the Damned...and it's also played outside everywhere from 2100-0000)
MM7, my favorite tunes are the ones played in Harmondale City, and also that one played in the Temple Of the Moon.
Twenty-plus years, and those two games are still as much fun as the first time I played them. Sure, the graphics are quite dated, but the story lines suck me in EVERY time; perfect way to blow off a rainy or snowy afternoon!