Rogue Amoeba (makers of cool sound tools, such as Audio Hijack / Pro and Airfoil) has released Fission, a unique sound editor that allows for "Lossless" editing of compressed (mp3, AAC) audio files. The compressed formats split up a sound file into a series of small frames (~1/40 of a second each), which are very difficult to manipulate independently. Most applications simply decode an mp3 or AAC file to uncompressed audio for editing, and then re-compress the edited sound for export. The additional re-compression step results in some sound quality degradation.

Fission allows you to perform simple edits (cutting, splitting, and fading) in the compressed domain (without having to uncompress and re-compress), resulting in no additional quality loss (of course, the mp3 or AAC files you started with are lossy formats to begin with), hence the quotes around "lossless". It is ideally suited for the editing and splitting of large compressed files recorded from radio streams (e.g., using Audio Hijack Pro or a Griffin radio SHARK). Fission also includes a "Smart Split" feature that can automatically segment your files by searching for silence (that typically occur before and after songs or commercials). Very cool!

The interface is extremely easy to use (simple for novices, but familiar to anyone who's ever used a sound editor). I do have two small feature requests: 1) The ability to add split-markers in real-time during playback would be really helpful, and 2) Allow time to be displayed in units other than just minutes:seconds (e.g., samples). Overall, Fission is a great addition to any Mac/audio/music-lover's set of sound applications.

UPDATE: I just heard from Rogue Amoeba that my first feature request is already there (choose "Split at Playhead" or Cmd-T). My mistake! So my revised (very minor) feature request is to make this keyboard shortcut a single key, or allow it to be user-assignable.