This is for putting one single track as main music for your map. It does not utilize the stock feature of music changing, and goes against the intended design of multiple cues for various action pieces in the match, but some people just want a single track playing.
Assume your map is DM-DeathRoom and we are importing the track Colossus.
Make a wav file 44khz - 16bit (22khz - 16bit may be smaller) ie: Colossus.wav Note: a smaller wav file will mean a smaller overall map package that your players have to download.
Use the generic browser
Import the wav into Unreal Ed. Package=DM-DeathRoom, Group=anything or leave blank, and name=Colossus.
Make sure you check bAutoCreateCue
You will now have your wav (Colossus) and a cue (ColossusCue) file.
To add your "UT Map Music" Right click in the generic browser windows for your package and select "New UT Map Music"
Once again package=DM-DeathRoom, group=anything or leave blank, and name should be unique (something different)
Then under the UT Map Music properties "UTMapMusicInfo > MapMusic" enter the cue file under "TheCue" for action, ambient, intro, etc. Note if you place your music piece in the Ambient line, it will play as ambient also. You should be able to leave this field empty and it will play as a normal music track adjustable by the music volume.
You now have a WAV, A Cue and a UT Map Music file saved in your package of DM-DeathRoom. Three seperate pieces, so please recognize their distinction. Wav > Cue > UTMapMusic.
You can right click the Cue file and select play to verify your track will work. Select stop to end playing. In addition right click your Cue file and select "Sound Groups>Music". This will set your Cue as a music track.
If the music is too quiet go to the cue properties and up the volume multiplier. The couple I've experimented with I upped to 20 instead.
In addition your music track should loop for 16 times by default. This may be ok for a 4 minute track (16 loops x 4 minutes =64 minutes of music). If you have a shorter track, or intend for your music to play longer, then you should up the loop count under the MaxConcurrentPlayCount in your SoundCue properties.
Another option for longer track play is in the "Sound Cue Editor" for your Cue files place a loop function between the speaker and the music as below.
Now we need to add the music to our level so it plays.
Under the main menu View > World Properties > WorldInfo look for MyMapInfo. There is a little blue triangle to the right. Click it and select UTMapInfo. It will dump a bunch of stuff in the map info area.
Go down to WorldInfo> MyMapInfo > UTMapInfo > MapMusicInfo and select your "UT Map Music" file located in the package DM-Deathroom
Save your map and you should now have music if you did it right. Your map size will be very large at first, but once you cook it, the file size should shrink. My test piece went from 50 meg to 11 Meg once it was cooked.
In addition this is for just for including the music with your map. I would imagine someone could embed all the old UT tracks into a single package and then you could point your "UT Map Music" to that package and select the cue file. But don't quote me on that, I have not tied it yet.
Many of the UT3 game tracks are in your Sounds folder under A_Music_PackageName. Most of these will already have the Sound and Cue created, so you just need to add your UTMapMusic to your level and point it to the SoundCue of the UT3 Music package. If you examine the A_Music_Arrangements package manyof the stock UT tracks "UT Map Music" are there and you can just point your world properties music info to this package.
You can take use of the ambient and action pieces if you want or find a whole track and use it for everything.
Thanks to Karmatized for some guidance in parts of this process and I suppose (just to be official) standard disclaimers of copyright and distribution apply.