Dual 3:1 / 6:1 unity gain mixer (for cv or audio) in 2hp.

dual 3:1 audio and cv mixer (up to three buffered inputs with a single buffered output).
output of top mixer is normalled to the bottom mixer to give a 6:1 mix.
outputs are phase correct (e.g. the output audio is not inverted).
the input signals are neither boosted nor attenuated (unity mixing). their resultant sum is the output. e..g. input 1: 2v, input 2: 4v, input 3: 3v

output1: 9v (input1 + input2 + input3 = 2v + 4v + 3v = 9v).