In the 1930s, Crosley designed a tone-volume expander circuit that would, in theory, add fidelity to the music that you were receiving from over-the-air radio AM transmitters. The circuit was said to boost the bass and expand the volume. It was used in some of their better 1930s Crosley console radios that are popular with radio collectors today.
I have no personal experience with the circuit because I do not service or work on Crosley radios, but a good friend of mine that services antique radios says that the circuit adds nothing of practical value and is tantamount to an early example of tech-snakeoil. Looking at the schematic, I am inclined to agree, but without any actual hands-on experience with the circuit, I would not want to prejudge it.
For those of you either servicing one of these radios, or who enjoy reading about esoteric circuit designs of yesteryear, [ this article ] from National Radio News, July 1936 issue, will be a good read. I scanned this article and cleaned it up with Photoshop as a courtesy to my readers.