(Song and Silence: A Guidebook to Bards and Rogues)

Illusion (Pattern) [Mind-Affecting]
Level: Bard 4,
Components: V, S, AF,
Casting Time: 1 action
Range: Close (25 ft. + 5 ft./2 levels)
Effect: Three illusory performers
Duration: Concentration + 4 rounds
Saving Throw: Will disbelief (see below)
Spell Resistance: No

This spell creates spectral accompanists.
They appear to be normal performers of any humanoid race (caster's choice) who back up the bard's performance by playing, dancing, singing, or any other means the caster desires.
They can also interact with others on a limited basis—
smiling, nodding, responding to questions with a few stock phrases, serving as dance partners, and the like.
These illusory performers grant the caster a +2 circumstance bonus on Perform checks for the spell's duration.
Choir is a Pattern, not a Figment—creatures that become aware of the accompanists' spectral nature can still see them.
However, not only does a successful Will save negate the bard's bonus on Perform checks with respect to that creature, it also imposes a -2 circumstance penalty on those checks for the remainder of the spell's duration.
Focus: The caster's instrument.