Mellotronists

Does anyone know why the stations were configured the way they were?
For instance, MkI RH keyboard, Station 4 has Trombone/Tenor Sax/Trumpet
but on the MkII, Tenor Sax appears with Brass and 3 Violins, while
Trombone was dropped altogether. Were the instruments just randomly
combined or was there a method to the madness?

The trombonist was fired for constantly being drunk on the job. No one wanted to play with the tenor sax because his vibrato was so wide, so they drew straws and Station 2 lost. The choir was out on strike at the time, so they were replaced by a scab Lowry organ. The mandolin was originally in the middle on Station 4 but complained so much about the obnoxious trumpet sound (especially that high F), that Les moved him over to the opposite end. The but an acoustic guitar on because an unacoustic one wasn't available. There also was supposed to be an Italian accordion, but the French accordion threatened to quit if it was included. Everybody else just sorted themselves out.