Casio SA Serier "note on" (gate) signal

[Rolbista]

I've come to a point in my life where I need an envelope generator to drive a VCF. The VCF processes the signal from a Casio SA 65 that is also fed through a comparator before it hits the filter. Now, I've been planning to just rectify the "comparator"-ed signal into dc and use it as gate. i'm afraid however,  that this method won't handle legato playing too well since I would also like to have an option of retriggering the EG with every key press. Is there a point in the SA-65 circuit that I could tap into to get a clean note on/gate signal? I looked at the service schematic and first thing that came to mind was the LCD driver which displays notes currently played, but I was unable to figure out a specific point on the pcb. http://elektrotanya.com/casio_sa65.pdf/download.html here's the schematic