In the early 1970s the market for blank cassette tapes was pretty cut-throat. US company Memorex was looking for a way to stand out, and hit on the idea of “shattering glass”. TV adverts showed singer Ella Fitzgerald breaking a wine glass, as Caruso had supposedly done as a party trick.

The Memorex twist was that Ella recorded to a cassette that was then played back to shatter the glass – with the slogan “Is it live, or is it Memorex?”

Hi-fi buffs were up in arms. They did not question the fact that Ella’s recorded voice could shatter a glass, if she hit a note that made the glass resonate, and playback was loud enough to make the resonance destructive. Memorex gave demonstrations to prove the trick worked, at public and trade exhibitions.

Witnesses were given certificates to prove that had seen a glass break. But they had to wear ear protectors.

What hi-buffs did not like was any suggestion that it needed an especially good tape to do the job; it would have been hard to find a tape that did not fit the bill. A technical paper released by respected audio consultants Bolt, Beranek and Newman in 1973 revealed that the sound level used was well over 140 dB, which is way beyond the threshold of pain.

After prolonged debate the UK’s Advertising Standards Authority approved the adverts saying “although it is most unlikely that this effect could be related to the domestic situation, the Authority took the view that the advertiser was entitled to emphasise the qualities of his product by describing how it might operate in exceptional circumstances.”

And Memorex – and Ella – had the last laugh. The slogan stuck until Memorex was sold off and run down in the 1980s. And it broadened Ella’s appeal at a time when rock music was ousting jazz.