The rights of springs
Invented by the Hammond Organ Company in the late 1950s specifically to accompany their own instruments, the necklace reverb was a lower-priced, smaller and much better sounding alternative to the oilcan spring reverbs that came before it.
Three springs of differing length were strung across the horizontal bar of a T-shaped frame, like a necklace, the shortest at the top, the longest at the bottom. The signal from the input transducer caused the springs to oscillate independently of each other, yielding a complex ‘modulated’ sound as the vibration from each one arrived at the output transducer on its own ‘timeline’.
Although it sounded fantastic, sadly the necklace reverb wasn’t around for long. The tendency for those loosely hanging springs to make horrendous clattering noises when shaken by accidental contact or heavy on-stage vibration saw it quickly supersed by tensioned dual-spring models.