I think that an important fact being overlooked is that for the listener, and even for many players, the "Mellotron" is not just looked at as an audio playback device, but that the individual sounds are perceived is instruments in their own right. I'm sure I'll love other string sounds available, but they will not supplant the 3-violins sound, they will supplement it. In the same way, the "strawberry flutes" is an instrument in and of itself, a hypersonic, polyphonic flute with some odd voicing peculiarities, idiosyncrasies that are part of the character of the sound and no other sound will ever replace it. It seems to me that the sound of each Mellotron tape set is as unique an instrument as a piano, and it's almost like the physical machine is just the delivery device for the actual instrument.