A few of the off the shelf drivers have a line in. I cannot attest to the speed of processing and resultant delay. I can say that the results are lackluster relative to what is possible with either software driven fft or use of something like this to process the analog signal. Part of that could be that what they choose to do with the data in terms of driving the LED portion seems to be fairly restricted in terms of scope and vision.
Of the 2, I like software fft as it allows richer analysis. I routinely get ~55 frames per second output with 16 bins of left and right data to a 4000+ element LED array.
To pull this off, I like the teensy 3.6 and the associated audio board. I also like their OCTO led driver if the array is big enough to merit parallel output ( which my setup often is).
