The reason for this is because at concerts, you can buy a piece of merch called a lightstick. Essentially, it is a STM32 and a mems microphone that is demodulating the carrier signal, so it can flash in time with the music. The tone has to be <ultrasonic because it has to work with consumer speakers and the mic in the device.
I assume the theory goes that anyone who has been to enough concerts to have a lightstick is no longer capable of hearing the noise.
On my Monday morning drive to work, I put on a CD by the band Cake, an album I'd listened to dozens, if not hundreds of times at this point, and would you believe that now, piercing through the mix, I heard the squeak of the drummer's kick pedal. Never noticed it before, but because I was so focused on those frequencies for two days straight, now it was all I could hear.
I switched to listening to purely electronic music that month, and I never noticed squeaky kick drums in studio recordings again.
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It's not like a single frequency buzz or carrier wave. It changes along with the pitch of the lyrics and clearly some kind of filtering they're doing to the voices. Either that or I'm paranoid and hearing things.
Having said that, I think what you might be hearing is actually another modern trend - which is just boosting the high frequencies in the vocal a lot. Pop vocals right now are mixed very 'bright', sometimes almost painfully so.
Also common to actually have multiple vocal tracks. Sometimes just a double singing the same thing, but sometimes it can be pitched up or down an octave, and I've also seen "whisper" tracks where a whispered vocal is layered with the main one to give it even more of that bright breathy sound.
Autotune is often present in almost any decently-high budget studio recording of loads of different genres. Its just not obvious.
Autotune doesn't need to sound like Cher in Believe or T-Pain in any song he sings or Kesha. They're just cranking some of the settings to make those super obvious artifacts. When a sound engineer uses autotune (or the many other similar effects) you wouldn't even notice its there.
Speaking as someone who moonlights doing live music production, autotune is used loads of places.
When Cher's Believe came out, autotune had been a thing for several years. Its just that most people thought people didn't like speed == 0 until Cher made it a thing.