Mastering is the final step that is made before printing an album – both in terms of technical and creative point of view: http://www.producerspot.com/behind-the-audio-mastering-process-tips-and-tricks-tutorial-article
JAMin is the JACK Audio Connection Kit (JACK) Audio Mastering interface. JAMin is an open source application designed to perform professional audio mastering of stereo input streams. It uses LADSPA for digital signal processing (DSP). JAMin is licensed under the GPL.