my suggestions:

The advantage of zipping the MP3 in a folder (directory) is that the user only need to download one file.

1- create a folder (directory)...example "mymp3"
2- copy the mp3 files to the folder "mymp3"
3- zip the folder. Usually a extension .zip will be added to folder, like "mymp3.zip" or "mymp3.gzip" or "mymp3.rar" (depend in what utility you use to ZIP or compress the MP3 folder).
4- Post "mymp3.zip" file in place where it can be downloaded.

Done

I can't give you more details, because I don't know what OS are you using, but the later steps are good for any.