Mellotronists

A question which may be asked before but I don't remember that. I'am asking myself how 
they've done the lower notes on the Flute (as far as I know the range of the standart flute 
ends at the C), so are the notes G - C from an alto flute or are they pitched? Our guitarist 
played the Tron Flute and had the impression that there is a change in the sound quality. I 
have never thought about how they have done the recording, yet... It's not such an obvious  
"gap" like the 'Cello below C.

Thomas