Definition from the article in Wikipedeia:

Sonification is the use of non-speech audio to convey information or perceptualize data.^[1] Auditory perception has advantages in temporal, spatial, amplitude, and frequency resolution that open possibilities as an alternative or complement to visualization techniques.

Musification is the sub-specialty in which the sound is musical.

Here at IAA, we regard Sonification and Musification to be applied, or functional arts. In the same way that a graphic artist would use her artistic skills in a commercial design project, a sonification artist would use her audio and musical skills as a means to an end -- to convey or represent information.