Here's a good online resource for those who don't have the software to convert their own music files (or are too lazy to get it):
http://audio.online-convert.com/convert-to-oggHere's a quick tutorial on how to use it.
1: Go to the website (duh) and scroll down to where it says "Choose a file to upload", and click that sucker. As an alternative, you can enter in a file's URL into the textbox below the button.
2: Then, scroll down some more and select a relatively low bitrate, select mono (mandatory), trim the song to the desired length with the provided buttons and boxes and suchwhat.
3: Lastly, click the button that makes the whole thing convert and download (in other words, the "Convert File" button), and there you have it! Now just rename the file and drag n' drop it into your Music folder (or pack it into an add-on).
For those who are a bit more serious about editing/looping/converting clips, use this software:
http://audacity.sourceforge.net/download/Here's a quick tutorial on how to convert you music to .OGGs in Audacity:
1: Open Audacity, click "File > Open" in the menu bar, and locate your music file on your hard drive.
2: Trim clip to desired length (optional; bu
t if you don't trim, remember, you can't post it here).
3: Edit clip/add effects (optional).
4: Make sure that the track is on mono, not stereo.
This is vital in getting your track to play in-game!5: Save file (optional; if you don't plan on working on this file again, skip this step).
6: Export your song by going up to "File > Export". Name your file, but keep it simple (no extraneous characters). Set export type to .OGG, and click export.
7: Add to your Blockland Music folder or package it into an addon, and you're good to go!
I hope this helps! If you have any questions, please ask.