WavePad offers one of the more robust, easy-to-use free audio editing tools for the Mac and it does so with the same powerful tools that the developers offer in some of their paid software. The result is a decent app that, while somewhat dated in terms of layout and interface, works as advertised and sometimes a bit better. If you are looking for a more powerful free editor, this may be it.
Installation of WavePad only takes a few seconds because of the small size of the file. It downloads and installs fast and once installed you can start editing files right away. Either create a new track or load a music file to start editing it, directly. You can then record audio to the track or start adding effects like echoes, fades, compressions, and more; and there are plenty of basic editing tools for clipping, moving, fading, etc. Other free tools include batch conversion, a small but decent free sound library, and tone generator and surround sound effects. The tools don't offer the kind of customization and options you'd find in a paid tool like the developer's very well-made MixPad, but it does offer a lot of tools you don't normally find for free.
If you are looking for a decent free audio editing tool for your Mac and don't mind the dated, at times frustrating visuals, then you'll enjoy what WavePad has to offer. It's fast, it's very light and portable, and it produces some decent sounding files, all within a single interface and for free.