I don't know what it sounds like, but I can imagine with a cartridge system and no attack....yuk!
And it looks like a dogs breakfast compared to the mellotron.
Actually for me the look of the tron was very much part of why it worked so well. Every concert I went to, where there was a tron on stage, loads of people would wander down to the stage to stare up at this white beauty and wonder what the hell it was!
Andy K