Audacity is a free software, cross-platform digital audio editor and recording application. It is available for Windows, Mac-OS-X, Linux and BSD. wikipedia.org

Mastering, a form of audio post-production, is the process of preparing and transferring recorded audio from a source containing the final mix to a data storage device (the master); the source from which all copies will be produced (via methods such as pressing, duplication or replication). wikipedia.org

A record producer is an individual working within the music industry, whose job is to oversee and manage the recording (i.e. "production") of an artist's music.

An arrangement of a musical composition is a reworking of a piece of music so that it can be played by a different instrument or combination of instruments from the original. wikipedia.org

Audio post production is the general term for all stages of production happening between the actual recording in a studio and the completion of a master recording. It involves, sound design, sound editing, audio mixing, and the addition of effects. wikipedia.org

Audio editing is the process of taking recorded sound and changing it directly on the recording medium (analog) or in RAM (digital). wikipedia.org

A film score (also sometimes called background score, background music, movie soundtrack, film music or incidental music) is original music written specifically to accompany a film.

An audio engineer is a specialist in a skilled trade that deals with the use of machinery and equipment for the recording, mixing and reproduction of sounds. wikipedia.org

Music is an art form whose medium is sound and silence. wikipedia.org

Audio restoration is a generalized term for the process of removing imperfections (such as hiss, crackle, noise, and buzz) from sound recordings. wikipedia.org

Music engraving is the art of drawing music notation at high quality for the purpose of mechanical reproduction. The term music copying is almost equivalent, though music engraving implies a higher degree of skill and quality, usually for publication. wikipedia.org