As UTPe says, you have to do a lot of reduction, and depending on the original quality and type of music will sound a lot worse.
Bad sounding music on a loop can drive you nuts, and is why many people play maps with the music disabled.
The old tutorials don't explain what you are doing, only how to do it, so you don't know why these things have to be done.
I wrote a new one a while back that covers reducing the quality and preparing the file in Audacity (so all OSs can use the same guide).
After you have done it once you will be able to do it with any audio tool you prefer, because you will know what you want to happen.
Tutorial ->
https://www.ut99.org/viewtopic.php?f=6&t=4472
As I have a modern PC and OS, I use the new OpenAL audio renderer from OldUnreal.
http://www.oldunreal.com/cgi-bin/yabb2/ ... 1399614690
The new version supports MP3, OGG, FLAC and many more tracker module formats including OctaMED (I have many MED files)
It gives twice the amount of channels (useful if more than 16 sounds are happening, so you hear it all).
The sound placement is more accurate so you can hunt easier, and more adaptive if you enable the "Sound Attenuation".
eg. The sound properties change when an object is between you and the sound, instead of just louder and quieter depending on distance.
Walk past a door or window and you hear the street sound change.
The now optional EFX addon gives mappers the functionality of the EAX profiles in the Creative Labs Galaxy patch.
By adding EFX zone actors wherever you zone, you can make convincing indoor/outdoor atmosphere, and you can tell if gunfire is outside, in a small room, a corridor or metal room. etc.
Even just adding 1 EFX actor makes a big difference in city sniper maps. The City streets EFX adds a nice bit of echo with the right sort of sound.
Note: If you want to use the simple option of just using a full quality OGG or MP3, you will have to include the renderer with the distro, or provide a link.