A musician is a person who plays or writes music. Musicians can be classified by their roles in creating or performing music:

* An instrumentalist plays a musical instrument.
* A singer (or vocalist) uses his/her voice as her instrument.
* Composers, songwriters and arrangers create musical compositions, songs and arrangements. These may be transcribed in music notation, performed or recorded.
* A conductor leads a musical ensemble. A conductor can simultaneously act as an instrumentalist in the ensemble.
* A recording artist creates recorded music, such as CDs and MP3 files.

A musician can be self-taught, or learn by formal education in a conservatory or by a private instructor or a guru.

Musicians can be amateur or professional. A professional musician is usually defined as one who is paid to perform, compose or act in any other productive manner related to music, and whose main source of income is this activity. Professional musicians may work freelance, enter into a contract with a studio or record label, be employed by a professional ensemble such as a symphony orchestra or big band, or by an institution such as a church or business (such as a jazz club or a bar).