Hi rzprk, I have the same problem as you. I guess I coded the same patch as you, when I send the message to Synapse, it crashes. Did you solve the problem ?

I have been using Max/Msp and that worked perfectly. I just can't have it working on Pd

I found the way of doing it reading this page.

http://en.flossmanuals.net/pure-data/ch065_osc/