Task: Question Answering
Input (English): Context: But I always knew when Doug was playing the tympani behind me because it was flawless . I have a memory of Doug playing the rudiments on the snare drum for a music class test . The younger drummers could only wonder at his humble performance as I watched from across the room , mesmerized . At heart , Doug was much more of a set player , a rocker , but his formal technique was amazing . 
Question: How can the narrator be so sure that Doug is behind him ?
Output (English): The narrator has heard Doug 's virtuoso playing before .