I do not think that Williams was performing on Certain Smile as a session musician as the score was recorded in Munich, Germany in July 1958 during AFM strike. Although there are two cues ("A Certain Smile" [vocal version] and "The Dance Orchestra") which were recorded in LA. Unfortunately the liner notes doesn't offer a musicians list. Regarding the orchestrations the Lalaland release does not mention Williams as orchestrator. Neither is Edward B. Powell credited, Newman's main orchestrator during his tenure at Fox.