two inputs

[lightningfingers]

is there any specific procedure for putting two inputs on an effect or can i just put two where there should b one?

[Samuel]

You should probably look into simple mixer designs and incorporate a summing amp

[smoguzbenjamin]

use a mixer/buffer IE use an opamp to 'blend the signals' Buffer both signals first to stop them interacting and then use another opamp to mix them in together. That's how I do it. Maybe a little elaborate but it gets the job done every time.

[gez]

When I was a kid, my brother and myself used to plug into the same amp using a little passive EH 'junction mixer' (I think that's what it was called, it was just a load of jacks in parallel if I recall).  We could each control each others volume/tone etc.  It worked but it was far from ideal!

It's better to do this with a circuit that utilises a 'virtual' ground (inverting op-amp for example), that way there's less chance of the two signals interacting with each other.

Have a scan for simple op-amp mixers and you'll get the idea.