Audacity for Mac is a powerful audio editing tool that surpasses default OS X tools. The downsides are a dated and sometimes clunky interface and a cumbersome installation process.
Pros
Which Audio Editor Do I Use? Audacity (Windows, Mac, Linux) This is the godfather of free audio editing software. You can multi track to an extent (have more than just one stereo track e.g. A full band recording).
Powerful and robust feature set: Audacity is loaded with audio editing, recording, and exporting tools that work in tandem with Mac's multimedia capabilities.
Free with regular updates for diverse uses: Audacity is a free, regularly updated tool with solid support from the developer. This means a solid core that works far better than some other free software suites in the same category, and a good alternative to somewhat limited tools like GarageBand.
Cons
Interface is dated and sometimes clunky: While Audacity's feature set delivers, it looks and feels a little dated compared to more modern software. In most cases this is purely aesthetic, but finding certain menus can be cumbersome in some circumstances.
Bottom Line
Audio Editor For Mac Os X
If you need a powerful, free audio editing tool for your Mac, Audacity is a great tool with which to start. While the interface could use some updates, you'll still get the bang you're looking for in your audio project.