See Lady Gaga’s Career-Defining ‘Sound of Music’ Medley at the 2015 Oscars [VIDEO]See Lady Gaga’s Career-Defining ‘Sound of Music’ Medley at the 2015 Oscars [VIDEO]Lady Gaga performed a medley of "The Sound of Music" songs at the 2015 Oscars and she totally blew us away.Ali SzubiakAli Szubiak