Quake3World

When I replace any song in Q3, it won't play ingame even though it's EXACTLY the same format (22khz PCM wav). There were no music error messages displayed in the console.

How (and perhaps why) are you trying to replace the songs?

By naming the songs to what song I want to replace and placing them into a new .pk4 (inside a music folder).

Some of the Q3 songs (like the fla songs) are too slow paced compared to the sonic songs

pk3, right?

TRY
create your own pk3 by creating a music folder,place your song using the same name as the song you want to replace that resides in id softwares pak1-9.pk3 files then zip your music folder.
Then rename the zip file to for example quake3guy.pk3 , place your user created pk3 file in the baseq3 folder.
bah .. even I'm confused now because it sounds like you have done this already

whats the name of the pk3?
i recall that quake3 loads pk3s alphabetical and in a cascading manner. not sure if pak0-9's are excluded from this process tho.

I placed the wavs into folder: music, which was then placed into a new pk3: pak13.pk3