Super Sound - Super Sound is a resourceful audio and music editor.
Matchering - Open-source audio mastering app that masters music based on any reference track you provide.
Audacity - Audacity is a free and open-source audio production software suite that includes a surprising array of editing tools and recording systems.
eMastered - eMastered makes a song sound better through online mastering.
Audio Video Editor and Mixer - Audio Video Editor and Mixer is a tool that helps you add changes to your video and audio files.
Audio Mastering - Pro quality, fully functional audio mastering application for iPad.