I mean yeah it makes perfect sense that they’d work.
Lemme tell you something, all matter in the universe (including our brains) are made of atoms, those atoms consist of sub-atomic particles, one of these subatomic particles is called “quarks”, and these are one of the fundamental particles that make hadrons (protons and neutrons).
Now these “quarks” are often called strings, and the string theory suggests that these quarks are actually tiny vibrations of energy, making them not really the actual Quarks, but more like the vibrational “glue” between the Quarks.
What’s my point here? These “strings” vibrate, and vibrations don’t just come from energy, but sound as well, and if every atom in your body and brain is essentially a mixture of many vibrating strings that are “glueing” all the other particles together, then it makes perfect sense that different frequencies will have some sort of effect on those “vibrations”, subatomic particles, atoms, and your whole being.