Using poly~ - What are the tricks?

I've understood from other users that the "poly~" object is a temperamental one

Don't worry, it only seems that way until you figure out how all the features operate; then all you have to do is not forget by the time you work on your next patch! ;)

There are two things you need to check out to get this to work. The voice allocation features of the and messages will send the arguments to the first instace of your poly~ subpatch that is not listed as busy. Max has no way of knowing what counts as busy for your particular patch, so you need to have a [thispoly~] inside your poly~ subpatch and send the appropriate busy or not busy messages to [thispoly~].

Any messages sent to your [poly~] without using or will be sent to the instance of the subpatch that has been most recently selected by the target messsage. If you have never sent a target message to your [poly~] the default is that instance 1 is targeted. Sending would route the inlets to instance 2, sending targets every instance and untargets everything.

So here is what is happening in your patch. Since you never use [thispoly~] to set the busy state of a subpatch instance, Max assumes the first instance is not busy and the note number is always sent to the first instance. Also, even if you were setting a busy state, you would find another bug because without using a target message to [poly~], any input to your middle and right inlets will be always sent to the first instance.

I would recommend getting rid of your middle inlet and instead use the message to send the note and velocity to [poly~]. Also, maybe use a [trigger] to first send to [poly~] before sending the Fundamental Frequency value. Although, I suppose in the case of this particular patch, you could use a [loadmess target 0] instead.