How do you make mp3 files smaller?

This can be done.. Like in Princess Prophecy RPG, and a few others.. There were many music theme songs in them.. and i know they can be made smaller so they can fit into the map size.. but how? I can't add anymore than 1 or if im lucky 2 diffrent music theme songs before it says the file is too big for bnet.. So can anyone help me here?

There are lots of ways to make file sizes smaller.
Lower the bitrate on your encoder. If you're encoding at, say 256kbit, try 128, or if that's not enough, go down to 112 or 96. 64 is usually too low for music.

Also, encoding as VBR (Variable Bit Rate) can help reduce file size. Try conservative settings, like 96 for low, 128 for high, and step down from there, if it's still too big.
At those settings, a relatively complex song at 3:00 will compress to about 2.5 MB, which still might be too much.
At min 64, max 112, the filesize will be appx 1.5 MB and is still somewhat passable.

(earlier, I gave erroneous advice about converting the wav, but this has been edited out)

Encode as MONO, and you'll reduce filesize some more. But not much!

Hope that helps.

John

PS If your conversion program doesn't offer these options, download CDEx, which is totally free and offers all these options.

Good post, John. :)
128 kps is the usual standard for mp3's.