(See the best response by LordAndrew.)
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Problem description:
This might look like a n00b question but does Dream Maker support MP3 files. I usually use WMA, but i didn't find any converter. If no, does anyone know any really good converter. Thank you!
Best response
You cannot play MP3 files in BYOND normally. A workaround is streaming an MP3 through a Flash player in a hidden browser element.

If you don't want to do that, I'd suggest getting Audacity which allows you to convert MP3s to OGGs (it might also do WMA too, but BYOND supports playing OGGs as well).

Edit: Audacity exports to WMA too.
Thank You LordAndrew! Sorry for my Lack of Sound Experience but what is better OGGs or WMA?
In response to Addmelol
I'm not for sure as I don't use WMA a lot. OGGs tend to be smaller than MP3s while still sounding about the same.
Thanks :)
Just in case you were wondering, BYOND doesn't support MP3 due to the licencing issues (which often relates to $).