Wave Editor

uses iZotope, which has the best frequency and time stretch conversion in the industry. Wave Editor also includes a clever editing system that lets you split the audio into sections. You can edit multichannel audio files without having to separate them first and allows you to draw Bezier curve-based fades. Supported audio formats include: MP3, AAC, FLAC, Apple Lossless, Ogg Vorbis, and so on.