At the end of the 19th century, Dr. Albert Abrams in San Francisco, a quite wealthy man, traveled to Europe for advanced medical studies. During that trip he watched the famous Italian tenor Enrico Caruso tap a glass to produce a pure tone, then sing the same note to shatter the glass. This led him to the idea that sound frequencies might be applied to medical conditions. This led over the years to a sequence of dramatic discoveries which resulted in his creating an electronic device that could send out frequencies which matched the tone frequency of a disease, and in the process cure the disease. Many people were treated successfully via his machines. After her death the spirit of Betty White (early episodes) explained to her husband in 1939 that everything in the material world has its own frequency, and that matter was "an arrested frequency," slowed down from the spirit world for our dense material world. The entity Seth in the 1960s and 70s explained much the same thing.