Comment by xhevahir
It's not modern instrumentation. It's a Technics arranger keyboard like the kind you might have heard in an airport smoking lounge. He started using them because they allowed him to build an arrangement without the help of other musicians. They've always sounded chintzy to me but they worked for him because of the cabaret nature of his songs.
His Technics is used in places, such as "Tower of Song". But "First We Take Manhattan" was recorded using a Synclavier, which at the time was as cutting-edge as you could get.