I need to mix 4 analog inputs with different weights into 4 analog outputs with audio application in mind. This can simply be made using potentiometers and opamps for buffering, like shown on the first pic for 3x3 matrix; I do understand that this schematic is not perfect in many ways (for example, you can't cut off any input completely), but it's good enough to demonstrate what am I trying to achieve.
However, I need to control the matrix digitally, say, using the I2C interface. This can be done using I2C digital resistors, but the schematic will just get huge and costly, as for a 4x4 matrix I will need 16 digital pots. And with even more I/O it just gets ridiculous.
So, my question is: Is there a way to make such a 4x4 controlled matrix (without D/A and A/D conversion!) more compact and cheap? Say, are there any ICs made specifically for this purpose? I could not find any.
EDIT: I've just realised that these digital pots are very rarely logarithmic, and that is kind of what I am looking for also.