 In 2004, Lewis was contracted by Aguilera to arrange her Grammy performance of "Beautiful", which featured a 21-piece string orchestra, the Roger Wagner Chorale, and her band.That night, "Beautiful" earned Aguilera the Grammy for "Best Female Pop Vocal Performance".In addition, Lewis was very involved in Aguilera's 2006 "Back to Basics" album as a vocal arranger and producer, string arranger, horn arranger, and was a co-writer on "Without You" (co-written by Christina Aguilera, Kara DioGuardi, and Mark Ronson), Lewis also traveled and collaborated with Aguilera as her musical director and arranger on her 2006-07 Back to Basics Tour and the tour DVD, "", and has also served as her vocal producer on numerous occasions and on records including "Tell Me", the lead single from Diddy's 2006 "Press Play" album.