Session singer

Session musicians, also called studio musicians, are professional instrumental performers who can be hired to play at live performances or in recording sessions. Many session musicians specialize in playing rhythm section instruments such as electric guitar, piano, electric bass, double bass, or drum kit. Some session musicians "double" on multiple instruments, such as electric bass and double bass or keyboards and guitar, a skill that enables them to play in a wider range of musical styles. Usually such musicians are not permanent members of a musical ensemble with the singers/soloists that they are accompanying and they often do not achieve individual fame in their own right as soloists or bandleaders. However, some backing bands of session musicians have become well known (e.g., The Wrecking Crew).

The term is applied to performers working in many musical styles, ranging from rock, R&B and soul music to country music. Versatility and excellent technique (having strong rhythmic sense, playing notes and chords correctly, excellent intonation, etc.) are two of the most important skills of session musicians, as they may have to perform songs, tunes and pieces from a range of different styles in a range of different settings, often with little or no rehearsal time or personal practice time. As well,session musicians have an extensive knowledge of musical styles and idioms.

For example, an electric guitarist recording a session is able to play stylistically appropriate chord voicing and "fills" in a 1930s Big Band jazz style, a 1940s Bebop jazz approach, a country music style and a hard rock style. Session musicians are expected to learn parts rapidly and they are often skilled in both sight reading and improvising chords or a bassline (depending on their instrument) from a lead sheet or chord chart (or, in country music, a song chart in the Nashville number system). Session players can often play in a range of musical styles. Thus, if a record producer needs to record the basslines for a group of songs in a range of styles (rock, R&B, country, jazz, etc.), she can do so by hiring a single session bassist. Session musicians can play accompaniment parts and solos that are either written out, learned "by ear" from a CD or record or improvised.

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Wikipedia