A great number of classic amplifiers, preamps, tuners and so forth have been dumpstered when so mounted because it was assumed they were the old brown goods consoles, good for nothing. Another sad fate are those that were built in to walls or counters and simply sheetrocked over when the house was modernized.

Another, not commonly remembered trend was the combining of the home hi-fi system with electronic organs and using the hi-fi as a PA. Hammond organs almost always were sold with Leslie speakers, but most of the other brands offered line out options and an installed system with a separate amplifier-sometimes as huge as the McIntosh MI200 or some Altecs running 211s-and three way speaker system. These installs are especially likely to yield choice bonbons such as Altec Duplex or Jensen triax drivers, Altec or JBL horns, Altec mixers, and so forth. Look for odd connectors in walls on these.

Organ systems were always full custom installs, but inhouse hi-fi (as separate from, but as with NuTone intercoms) often will appear in all the houses in a subdivision built out between the late fifties and mid-60s. When something quit, the whole system fell into disuse due to the awkwardness of troubleshooting and sat unused until ripped out or covered over during a refurbish. A lot of “moderate midcentury moderns” were ‘updated’ in the late 70s and early 80s when all that “dated Jetsons crap” was considered just old and dorky.