Embed tone into music

I see some videos on youtube where i can’t hear any tone in them (even if i turn the volume up) but when i measure the frequency they match the frequency that the video says it contains. Does anyone know how they do that?

What? “Tone”? Do you mean you don’t hear any sound at all? What are you expecting to hear? A single tone, like for testing/tuning? Or is speech or music?

How are you measuring frequency?

By tone i mean something like 432hz or 440hz. When you generate a tone through audacity you can hear it below the music. But this doesn’t happen in the videos.

I’m measuring it through the sound analyzer app for android.

Audacity has spectrum-analyser tools …
https://manual.audacityteam.org/man/plot_spectrum.html
https ://manual.audacityteam.org/man/spectrogram_view.html

[Further reading … Solfeggio frequencies - RationalWiki]

By tone i mean something like 432hz or 440hz. When you generate a tone through audacity you can hear it below the music. But this doesn’t happen in the videos.

I don’t know what videos you’re talking about…

And, I don’t know what you mean by “below the music”. If you simply generate tones there is no music unless it comes from somewhere else. If you mix any constant-frequency with music it’s going to sound pretty-bad and some notes will be dissonant (“sour notes” or out-of-tune). For example, if you play an A and an A-sharp (466Hz) at the same time they will sound dissonant. If you play any two keys on the piano that are next to each other you get dissonance. If you play two keys with one skipped in-between it sounds harmonious. It’s the relative pitch between notes that’s harmonious or “magic”, not the note or frequency by itself.

Despite what you may be reading, there is nothing “magical” about 432Hz or 440Hz. If you want to listen to those tones you can generate them and listen to them all day long, but it’s pretty boring! And in a blind listening test without a reference, most people can’t tell if they are listening to a 432 or 440Hz tone. I can’t, and even someone with “perfect pitch” might misidentify 432 as a normal A (the next-higher normal-note or A-flat (the next-lower normal note).

All “normal modern Western” music is tuned the to the A=440 standard. It’s simply a tuning standard so all of the instruments in the band/orchestra can play in-tune. But, that doesn’t necessarily mean that the song is in the key of A or that there are any A-notes in the music at all!

Of course, there are several A-notes on the piano. A4=440Hz, A1=55Hz, A2=110Hz, A3=220Hz, A5=880Hz, etc. With standard tuning, 432Hz isn’t a valid note. [u]Table of Notes & Frequencies[/u].

Some instruments can be re-tuned and some cannot so it’s important to have a universal standard. You can re-tune a piano but it takes a long time. If you’re in a “guitar band” or if you sing acapella you can tune & play/sing to A=432 or use any other non-standard tuning but most professionals stick to the standards.

All natural sounds contain many simultaneous frequencies. Only pure sine waves contain a pure 432 or 440Hz tone. The “pitch” or “note” that you perceive is usually the lowest and most dominant frequency component. If you are listening to music or speech the dominant pitch will change from moment-to-moment and you might not see anything useful on a spectrum or with a “frequency measurement”.