Sing Wah...LFO problem

[Ry]

I built a Sing Wah from RG's design on a breadboard a couple years ago and wasn't too pleased with the results.  I was recently thinking about what a great idea it was, so I dusted off the breadboard and fired it up after work.  To my great surprise, it still worked after 3 moves!

After playing around with it for a while, I realized what was wrong with it, the two sequencers (4051's) are switching outputs asynchronously.  As soon as one switches, the other switches, rather than having both switch at the same time to create the vowel sound...so it sounds like two Seek Wahs going at different speeds.  It's a neat effect, but not quite what I'm looking for.  

Any ideas on how to force the 4051's to lock up in their switching?

Ry

[Maneco]

hi,
if the a,b and c select input of the 4051 are tied together,they must change the output at the same time