But this one: http://www.image-line.com/documents/flstudio.html

It's very good to use if you want to make your own music for your mod, and it's fun to use. I tried it, very powerful software, take listen here.

You can buy a iPad version for $20. or download a demo for windows http://www.image-line.com/downloads/flstudiodownload.html

For those who don't have money, free / open source / multti-platforms softwares:

LMMS

Amazing possibilities, but a good knowledge in music theory is required.


or this one:

Jokosher

more easy to use but less possiblities

Sound Editor:

Audacity

have fun !

A Cubase/ProTools like? REALLY expensive tools.

Just another thing about LMMS: It's off course made for composers, means that you have to "write" your music/sequence and choose the appropriate sounds for it, I think using this program was not made only to work with samples, it would limit the use of LMMS in my opinion, and as any specialized software, an "apprentice" stage is needed to understand all features. An example: I understood absolutely nothing in 3D editing softwares.
And of course, to obtain the best results, you have to edit your own sounds but there are a lot of compatibles free-to-use samples available on the internet.

Another solution:

Rosegarden

The best in my opinion, the Cubase/ProTools users will love it !
But unfortunately, under Linux platforms only


Yeah, Audacity allows to convert almost everything. But you can also edit new sounds, edit samples, change tonality/pitch, speed, enhance or reduce some frequencies, etc...

Avid user of FLS, it's what I do all of my producing on!
Here's a collection of tracks I've done inspired by Freelancer and other general space themes.:
http://www.youtube.com/playlist?list= ... rLeEQK6pfCdGOHwwExEALntkI

EDIT: The latter two tracks are more what you're probably expecting out of that link, Sendei and Senseki Station are both very experimental.