Kesinlikle "Stüdyo Müzisyenidir".

http://en.wikipedia.org/wiki/Session_musician

Session musicians are musicians available for hire, as opposed to musicians who are either permanent members of a musical outfit or who have acquired fame in their own right. Although the term generally refers to musicians skilled in contemporary musical styles such as rock, jazz, country, pop, etc., it can also be used to describe musicians from classical and other traditional styles.

Session musicians are used in any situation where musical skills are needed on a short-term basis, ranging from a few hours to many months. Typical uses of session musicians are:

In a recording studio to provide backing for advertising, film and television music
To provide instrumental or vocal backing for established solo artists or groups, both in the studio and in concerts and appearances
To act as temporary replacements for permanent members of a band or ensemble
To provide additional instruments or vocals when needed by a band or ensemble
In ensembles for theatrical productions
The term generally does not refer to:

Recording artists
Solo musicians or ensembles (without recording contracts) who give public or private performances for hire by themselves, such as wedding singers or bar bands
Amateur musicians
Full-time members of professional ensembles, such as symphony orchestras
Sideman

Instead, session musicians perform with (and are hired by, or on behalf of) some other musical act or artistic production. Apart from being highly competent at their instruments, skilled session musicians are also expected to learn parts rapidly, and to play music by sight (reading directly from the musical score).

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Note added at 10 days (2007-08-16 08:44:06 GMT) Post-grading
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Sanırım bir düzeltme yapılmayacak. Moderatörler ilgilenmiyor.

Session müzisyen aynı zamanda geçici eleman eksikliği olan sanatçı ve grupların canlı performanslarında veya kayıtlarında çalmaları için görev alan müzisyendir. Bazı durumlarda beste/aranjman vb. resmi üyeler tarafından yapılan ve stüdyoda kaydedilen ancak canlı kayıt esnasında bir kişi birden fazla enstrüman çalamayacağı için sadece konserlerde çıkıp şarkıları çalan resmi üye olmayan müzisyenlere de denir. Bu durumda stüdyo müzisyeni terimin tüm karşılıklarını vermiyor.