The 74LS624 should be fine, as I only want a pitch bend of a couple of notes, for tuning adjustment.
Actually, I've just thought of an idea that might be interesting to try. Looking at the schematic you provided of the circuit, I presume you control the frequency by the input CV voltage from 1-5V, controlling it by a pot from a 5V DC source - basically using a resistor to control the CV.
If I can get pitch bend control using this, perhaps I can control the pitch bend using pressure. For example, using a pressure/resistance device on the mouthpiece that could bend the pitch the harder you squeeze, if you clamp down on the mouthpiece with your lips. Are there any of these things available? - I'm thinking maybe a semi-conductive rubber strip on the outside of the mouthpiece, that changes resistance as pressure is applied - is there such a thing? It would need to be made slobber-proof as well
Cheers and thanks for your help
Graham