"When I Say So" - Written by Brian Kierulf, Britney Spears, Joshua M Schwartz, and Brian Wayne Transeau (BT). Produced by BT, BT has also referred to it as "'Til I Say So." Also rumoured to be saved or re-recorded for "In The Zone," but there is no confirmation of this. An interview stated "BT describes his other contribution, 'Till I Say So', as an 'upper-mid-tempo new-school break-beat track, with guitars and live drums and some of my crazy-ass stutter edits'.
SOURCE some people in the comment board posted the link and left that information. When I Say So