Was just thinking back ('67 Mustang again) and remembering I had to save for 2 weeks to buy this reverberation unit. Pretty nice, wood grain front with this big spring (for real) that was used for a sound delay to a rear deck speaker (only one). The radios were mostly AM only back then and stereo wasn't really born as yet. Yeah there was Hi-Fi and a few 78rpm's around but nothing broadcasted (was Maine).

So you had the mono front speaker and mono rear and it made the entire car sound like a big echo chamber by playing the rear speaker time delayed (adjustable also). I loved it, still think it was better than today's stereos, meaning the sound not high wattage.

Before tape players the elite setup was the upside down 45 rpm record player. Those would be mounted under the dash and had a slight pressure applied at the needle to keep from skipping driving down bumpy roads. So in a huge car like a '63 Bonneville you'd hardly know it was there.