@cheezmaker Try [list prepend] for vanilla in place of [iem_prepend]
Because connections will be lost to unfound objects when you open a patch, your best bet is to open them in a simple text editor and do a search and replace.
In ctl-bank-abs.pd you should replace [prepend] with [list prepend]........ it is full of [prepend] objects...... not [iem_prepend]..... so the error is strange.
David.

@whale-av thanks for the tips! I changed the [prepend] objects to [list prepend] and realized it was probably thinking the [prepend] were [iem-prepend] because I have iemlib as an external library loaded on startup (so when I make a [prepend], the help box is from iemlib). The other error (Cyclone: please use [mousestate] instead of [MouseState] to suppress this error) shows up upon opening both the mono and poly synths, but the mono works anyways. No other errors are appearing when I open the poly version. Still not getting any sound.... Incidentally, I also installed pd-extended to see if this would work there, and the monosynth worked as well, with no error messages, but the poly didn't. Strange, but such is the pure data lyfe.