Sound Studio from Felt Tip, Inc., has long been a favorite of musicians, engineers, and just about anyone else who likes to record and edit audio. The latest version, Sound Studio 4.5.x, supports Retina displays, full-screen usage, multi-touch gestures, and a number of other UI refinements.
Sound Studio 4
On the audio end, Sound Studio 4 offers many high-quality processing capabilities, including a long list of filters and effects, crossfades, chorus, and delays. It even lets you play recordings backwards, so you can find out if Paul is really dead, or create your own hidden messages in your audio tracks.
On a more practical level, Sound Studio 4 provides filters for cleaning up pops, clicks, and other noise often found in musical tracks recorded from LPs. It also includes a normalize function that can be very helpful for those of you who create podcasts or radio streams.
Sound Studio 4 is $29.99. A 15-use demo is available.