Here's a problem that is causing me some grief. I'm rusty with electronics
these days, perhaps the experts in here can give me some pointers ?

I want to combine the audio outputs of an unspecified number of op-amps, say
2-20. A simple mixer would do the trick...except I need the resulting summed
audio level to be constant as outputs are connected to and disconnected from
the system.

I know a virtual ground is the standard method to mix audio but there's
another wrinkle here. I also need to send the summed audio signal to an
unspecified number of outputs, between 2 and 20. In other words, the common
point where all of the audio signals are present needs to be level
insensitive to changes in numbers of audio inputs *and* outputs.

Is this possible ? I've tried some breadboarding and find that each added
input results in a level drop at the "star point". Also, adding a second
virtual ground output completely kills the audio. I can, of course, add as
many outputs as I wish using the output op-amps as high impedance buffers,
which leaves me with the input summing problem.

Note...the electrical "star point" is not a physical point. In practice the
inputs/outputs are distributed along a common cable, of unspecified length,
which can change.

Comments appreciated, other than "design yer own f****** stuff", of course
:-) Just pointers to info would help.