Well, I've read other people saying its okay. I just downloaded it, no problems so far. If you want to put videos on YouTube with it, you have to download an exporter system that comes with it. Its safe too. So don't worry.
There is a version of Audacity for Mac OS X (See links below).
Mac, and more specifically Garage band. Or audacity if your publishing it to any were except iTunes.
For Windows, I would check out Audacity for basic sound editing and Wavelab Essentials for more mastering abilities. For Mac, Audacity and Peak LE.
Minecraft is safe to download for Mac, if downloaded from their site.
Audacity is one of the best free programs for recording out there, and you can find a Mac OS X binary at the official site: http://audacity.sourceforge.net/
There are many apps that will let you layer recordings. A good free one is Audacity.
There are a few programs that you can use on your computer to make mixes. If you have a Mac, GarageBand is an excellent tool that even supplies extra sound effects and musical items. If you have a Mac or PC, Audacity is a free program downloadable from the internet (just Google it) that does most of the same things. In some respects, they are the same, but GarageBand adds extra sounds better than Audacity, and Audacity can edit the existing sounds better than GarageBand. The only drawback to Audacity is that you have to record the sound live, you can't use a CD, but if you play the CD and record it, it works the same. Be sure to watch out for copyright infringement.
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The word Audacity is a Noun.
No. Audacity is completely free and legal.