I have been porting my Pd(2Live) abstractions over to Max for teaching and performance purposes (I am not defecting). An object which I rely on quite substantially in Pure Data is the [pitch] object by Olaf Matthes, which organises incoming MIDI note numbers into pitch-class, pitch-class distance and register. This is a useful abstraction for organising incoming instrumental pitch data tracked by FFT-based objects such as [sigmund~] or [fiddle~].
Olaf kindly sent on the .c code from which to re-create his object as an abstraction in Max.
I also recreated the the object as an abstraction in Pd.
You can download all the files as a single zip file from here. Please send any suggestions to info at rickygraham dot net