I finally decided to see what DoomRL would be like with music. So I downloaded all the mp3s, setup the config files, but when I try to run doomrl (i386 or x64) it fails and I get an entry in my error.log that looks like this:
Since it appeared that mp3s weren't going to work, I decided to try converting them all to ogg files. Surprise! DoomRL now runs with music for the first time in years. Given that it wasn't a quick fix, I wrote a shell script that downloads the mp3s, converts them to oggs, then makes the correct config file changes. The only real difference was that instead of using '0  - intro.mid' for the starting music it grabs the Doom II intro music instead. Here are the contents of get-ogg-for-doomrl.sh:
#!/bin/bash
# You'll need grep, sed, awk, wget and sox with mp3/ogg support
# You can get much higher quality Doom MP3 tracks from
# http://www.sirgalahad.org/paul/doom/
URLSTEM="http://www.sirgalahad.org/paul/doom/mp3/"
echo "Music = {
	start     = \"ogg/d2title.ogg\",
	interlude = \"ogg/d1inter.ogg\",
	bunny     = \"ogg/d1end.ogg\",
	intro     = \"ogg/e1m1.ogg\",
	hellgate  = \"ogg/e1m8-e3m4-e4m1.ogg\",
	level2    = \"ogg/e1m2.ogg\",
	level3    = \"ogg/e1m3.ogg\",
	level4    = \"ogg/e1m7-e2m5-e4m8.ogg\",
	level5    = \"ogg/e1m5-e4m4.ogg\",
	level6    = \"ogg/e1m6-e3m6.ogg\",
	level7    = \"ogg/e1m4.ogg\",
	level8    = \"ogg/e1m9-e3m9-e4m9.ogg\",
	level9    = \"ogg/e1m1.ogg\",
	level10   = \"ogg/e1m2.ogg\",
	level11   = \"ogg/e1m3.ogg\",
	level12   = \"ogg/e1m4.ogg\",
	level13   = \"ogg/e1m5-e4m4.ogg\",
	level14   = \"ogg/e1m6-e3m6.ogg\",
	level15   = \"ogg/e2m2.ogg\",
	level16   = \"ogg/e2m4-e4m6.ogg\",
	level17   = \"ogg/e2m6-e4m7.ogg\",
	level18   = \"ogg/e2m7-e3m7-e4m5.ogg\",
	level19   = \"ogg/e2m9-e3m1.ogg\",
	level20   = \"ogg/e3m2-e4m2.ogg\",
	level21   = \"ogg/e3m8.ogg\",
	level22   = \"ogg/e2m2.ogg\",
	level23   = \"ogg/e2m4-e4m6.ogg\",
	level24   = \"ogg/e2m6-e4m7.ogg\",
	the_chained_court = \"ogg/e1m4.ogg\",
	halls_of_carnage  = \"ogg/e1m9-e3m9-e4m9.ogg\",
	hells_armory      = \"ogg/e1m3.ogg\",
	hells_arena       = \"ogg/e3m2-e4m2.ogg\",
	spiders_lair      = \"ogg/e2m7-e3m7-e4m5.ogg\",
	city_of_skulls    = \"ogg/e1m5-e4m4.ogg\",
	the_wall          = \"ogg/e2m4-e4m6.ogg\",
	unholy_cathedral  = \"ogg/e2m6-e4m7.ogg\",
	the_mortuary      = \"ogg/e3m8.ogg\",
	the_vaults        = \"ogg/e3m5.ogg\",
	the_lava_pits     = \"ogg/e3m8.ogg\",
	tower_of_babel    = \"ogg/e2m8.ogg\",
	hell_fortress     = \"ogg/e1m8-e3m4-e4m1.ogg\",
	dis               = \"ogg/e3m8.ogg\",
	victory   = \"ogg/d1readme.ogg\",
}" > musicogg.lua
mkdir ogg
for ANMP3 in $(grep "= \"" musicogg.lua | sed -e 's/.*ogg\///' -e  's/\",//' | awk '!x[$0]++')
do
    MP3NAME=$(echo $ANMP3 | sed 's/ogg/mp3/')
    wget -P ogg "$URLSTEM$MP3NAME"
    echo "Converting: $MP3NAME"
    sox ogg/$MP3NAME -t vorbis ogg/$ANMP3
    rm ogg/$MP3NAME
done
sed -i 's/dofile \"music.*$/dofile \"musicogg.lua\"/' config.lua
Just download it and run it from your DoomRL directory then assuming I didn't screw up (it worked for me) music should play fine. Still no idea why the mp3s weren't working.