Have you ever listened to a badly mixed song with a persistent high-pitched whine undercutting part (or all) of it? Certainly that's not on purpose either, but I doubt anystudio equipment is giving off an intentional "test" whine either, so I've always wondered how that ends up happening.
I've got an example of this: Some Blackpink songs (cannot remember which ones, possibly Playing With Fire or DDU-DDU-DDU) were mastered and released on Spotify/iTunes [unsure if has been removed now] with a 18-19kHz carrier tone (iirc it was actually a number of tones) modulated. The signal was very loud. I first noticed this in a friend's car and assumed it was because the song was ripped from YouTube, but later realized that all of the versions have this.
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.
Sometimes it's old ears, sometimes it's the people in the room being oblivious to it from hearing it too much. I tell the story a lot about kind of the inverse of this - I was mixing my band's (terrible) recording, and during a weekend of mixing, I heard the squeak from my cheap kick pedal, like an icepick to the brain, piercing through the mix. I did my darnedest to EQ it out, and felt pretty good about it in the end.
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.
This happened recently on Taylor Swift's rerecording of 1989 - a persistent tone at 15KHz on multiple tracks [0]. The Taylor's Version records have to be some of the most carefully-produced albums around, given that the goal is to accurately reproduce existing recordings, so it's amazing that it made the final release.
It's surprisingly common in older music. I assume it's because recording studios used to run SD CRTs and everybody working there had already lost their high-frequency hearing. A 15.68kHz (mid way between PAL and NTSC horizontal refresh frequencies to remove both of them) notch filter fixes the problem in most cases.
Whenever my daughter puts on recent pop music, I can tell instantly. Every pop song singer seems to have their voices artificially boosted into one or two higher harmonics. It's hard to describe in words but instead of the singer singing a single note, it's as if she (and it's very evident with female singers) has some very, very high pitched harmony automatically added, which lasts the whole song.
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.
The other comment is right that autotune is almost always present in recent pop vocals - even when the singer is excellent, a little bit is now commonly added to give it that certain sound.
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 almost always present in recent pop vocals
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.
I've noticed some FM stations have an odd metallic ringing noise in the background - especially country for some reason. I'm fairly certain it isn't intentional.
