Nothing will get you in the holiday spirit faster than an iMac, a Commodore 64, a ZX Spectrum, and a Mega Drive singing a carol. Likely, James Houston of The Glasgow School of Art arranged this harmonic ensemble of synthesized voices for the novelty factor. After all, hearing the voice of Fred of Mac fame sing the words “Merry Christmas” would make any grinch’s heart grow six times the size. But it also serves as an apt lesson in he history of voice synthesis. There’s plenty of interest in the future of voice commands these days, with Joaquin Phoenix’s Her releasing…