Amy is shocked at a revelation from Sheldon after she buys him a new laptop. Also, Koothrappali sells out Leonard and Wolowitz after they lie to their wives in order to attend an early screening of a movie.
Taps (Bugle Call - Signals That Unauthorized Lights Are To Be Extinguished. This Is the Last Call of the Day) — US Army Band
Sheldon plays this as Amy arrives at his apartment just as his laptop dies.