Gmr_Leon: Um...What this fellow asked, please. I've messed around with DOSBox before, but in my experience, each game has required different approaches to configuration to make it work completely (or almost completely) correctly.
Forgetful: I had the same problem on Mac OS (can't help with Windows 7, sorry). You need to change the line
"populous Vga Roland MT-32" to "populous Vga Adlib" in the file
Populous.app/Content/Resources/Populous.boxer/C.harddisk/SINGLE.BAT
Unfortunately, even the Adlib sound effects are nowhere near the Atari ST sound I remember from Populous.
Thanks for the response! Unfortunately it occurs to me that this thread may not have made much sense to me as I was thinking specifically of Populous
2 and forgot this forum was for the series as whole. I get the sound effects and everything, but no music in 2, which may be attributable to the same issue as the OP was having, but I'm not so sure.