Is he singing?

Ipapa and I notice that Iden is singing lately. Can't be? Well, maybe the following events can prove that he is indeed singing? Ipapa introduced Iden to Schnappi CD since December last year - http://en.wikipedia.org/wiki/Schnappi. We will try to let him listen to the CD when he is in the car. Iden has this CD to accompany him most of the time during his car journeys. The second track in the CD is called Mahlzeit (http://www.amazon.de/exec/obidos/clipserve/B0007NOL5A001002/303-3035901-7408234). In this song, there is mention of the phrase 'Ma Ma' (Schnappi is calling out to his mummy). During one of the usual journeys back from his grandparents place, Iden was listening to the disc again. Then out of the blue, when Mahlzeit came on, he went 'Ma Maaaaaa". Both ipapa and I looked at each other and at that instant, we realised he knew the song! He was actually copying Schnappi to call his mummy in a high pitch and off he went "Ma Maaaaaa". It was a pleasant surprise to us. Then on a few other occasions when we were listening to YES 93.3, he was also trying to sing along with the singers. Of course he could not string the words together, but he would hum along when there are phrases like "la, la, la" or 'oh, oh, oh". And if you ask him to sing now, he will go "na, na.....". So.... can we term this as singing then?