John Mayer Battle Studies. Mayer's fourth studio CD debuted top the Billboard charts upon its 2009 release. This matching folio features Piano, Vocal and Guitar transcriptions of the singles Who Says, Heartbreak Warfare and nine more: All We Ever Do Is Say Goodbye; Assassin;Crossroads; Do You Know Me; Edge of Desire; Friends, Lovers or Nothing; Half of My Heart; Perfectly Lonely; War of My Life.