weird piano notes played when using midi to control eq three

[sdy]

i've assigned my edirol pcr-30 piano keys to control my eq3 in the master channel. when i press the key to turn any gain off it's fine, but then when i press it to turn it on... there is a loud piano note that is played and sustained for a while over the track. I don't have the controler linked to an instrument so I'm confused why the note is played. argh