There is a device called the Mosquito that shopkeepers use to deter loitering youths. It emits a high-pitched tone that teenagers find infuriating but adults cannot detect because our hearing declines in our 20s.
Civil libertarians are in a flap about it but the implications for pop music are also profound. If there are sounds that only teens can hear, then surely there must be songs that they get while the rest of us look on blankly.
I put the theory to the test by checking out the US and UK top 10 singles in search of high-frequency acoustics. They don’t take long to find. The current number one in the US is “Glamorous” by Fergie, singer with the Black Eyed Peas, which at first listen comes across as leaden-footed R&B but on closer inspection is found to have all sorts of high-pitched beeps and squeaks going on in the background, as if hinting at some parallel song just outside the range of adult hearing. Perhaps the youngsters who propelled it to the top of the charts know something I don’t.
At number two in the US charts there is a song immodestly entitled “This Is Why I’m Hot” by a rapper called Mims. It is an odd track. While Mims’ explanations about why he is hot are tedious – “I’m hot ‘cause I’m fly/You ain’t ‘cause you’re not”, the tautological rapper insists – a spooky, upper-register synthesiser line in the background makes the song almost subliminally compelling. Alarm bells and the odd piercing bout of whistling add a jolting sense of estrangement to the mix. This adult listener was left feeling both impressed and alienated.
Calvin Harris’s “Acceptable in the 80s”, the UK number 10, appears to have been designed to illustrate the fact that teens are better at picking up higher frequencies. It is a bouncy synth-pop number in which a variety of shrill sound effects compete for our attention, while the young shaver Harris – a Scottish teenager who originally recorded the track in his bedroom – croons in a falsetto: “I’ve got hugs for you if you were born in the ‘80s”. For those born in the 1980s or later, it is doubtless catchy as hell. For those of us of a more senior vintage, it grows more irritating with each listen.
The next step presumably will be to make a song discernible solely to the under-20s. Actually, that has already happened. Last year a ringtone was released using the same technology as the Mosquito, the idea being that only kids would know when their telephone was ringing. A dire spin-off dance music single followed using two sets of harmonies: one audible to everyone, the other pitched too high for adult ears to notice.
When I tried listening to it I developed a headache, which suggests the generational divide is not so neat, but if the technology can be perfected it will have startling consequences.
One will be the rebirth of the hidden message. In the past, these were invariably the product of over-heated imaginations, such as the belief that the cover of Abbey Road proved that Paul McCartney had died and been replaced by a lookalike, the evidence being that the McCartney clone pictured crossing Abbey Road was barefoot, out of step and smoking a cigarette in the wrong hand.
Then there were the equally implausible attempts to prove that certain heavy metal records played backwards contained elaborate messages of support for Satan, designed to implant themselves in impressionable teenage minds.
These were fantasies, but now the means for delivering hidden messages is a reality; hidden tunes too. In an age when pop’s demographics stretch from six-year-olds to sexagenarians, the old gulf between teens and adults is reopening: they can hear things we cannot.