Today he asked nanu to put on the headphones and to play some music. Nanu, but obviously, obliged and played a song. After listening to the song for 5 seconds he said "yeh to achha nahi hai".
So Nanu played another one but again was rejected by Betu as "achha nahi hai". This kept happening for the 5-6 songs and then betu declared "aapke paas to purane gaane gaane hain" in a very matter of factly tone. :) We all had such a laugh! And Nanu replied back saying "an Nanu bhi to purane hain!"