Hm… see the the thing is, anon, I don’t think Gelel is actually music so much as it’s just Shikako’s way of interpreting it. I’ve previously ranted about Shikako’s chakra sensor abilities here, and how, because of her “hypersensitivity” diagnosis she’s able to sense and differently interpret a larger spectrum of chakra/energy.
Unfortunately, I did also liken Shikako’s chakra sense more with touch and “normal” sensing abilities with hearing, which is incompatible with the why she interacts with the Gelel energy, but I think it sort of applies. Like. Literally no one else in the group could perceive Gelel–and I know, in comparison, that Shikamaru isn’t a sensor and Naruto (and probably Gaara as a fellow jinchuuriki) has issues with chakra perception mostly because he himself is such a large source of chakra it’d be like trying to listen for another car’s music when you yourself are an ambulance blasting sirens–but what about Temari and Kankurou? I’d actually think that Kankurou has some sensing abilities (maybe not on par with a Yamanaka) but close enough. And yet, nothing.
So Gelel’s energy is probably closer to natural energy on the spectrum that is… energy. Like. Chakra is a combination of physical and spiritual energies, then there’s natural energy, then there’s life force/souls/etc. So all chakra sensors (and even most non-sensors) can sense chakra. They can also sense physical energy (which is what a lot of Lee and Gai’s techniques are based on) and spiritual energy (which probably contributes to things like killing intent and such). Most chakra sensors cannot sense natural energy. It’s “outside of their frequency” so to speak, though people can become sages and be trained in sensing and using natural energy.
Life force is something else, not even Shikako can sense it (as we’ve seen in the Land of Hot Springs arc). She knows something is missing and something is being drained from her but she can’t feel it, where it comes from, where it’s going. All she knows is that it’s been taken and it’s going to take a long time before it’s fully restored.
Probably Gelel is somewhere between natural energy and life force. So Shikako can’t feel it the way she can with regular chakra or even natural energy (she can feel it in the air, drowning her lungs, pressing down on her skin like humidity, etc. etc.) but she can still perceive it to some extent. And I probably shouldn’t keep extending the analogy of Shikako’s sensing ability = touch vs. normal sensing ability = hearing, because that’s only to liken chakra sensing (which is obviously not something we have in this world) to senses that we can relate to, but Gelel is, again, something outside of normal sensors’ range of frequency. But still something that Shikako can perceive/interpret.
You know how there’s certain notes where humans can’t actively hear it, but they still subconsciously notice it or get affected by it? Like the fear frequency or cats purring, etc. etc. Gelel is probably like that. Or, well… maybe its more like. It’d be as if she’s “feeling” the vibrations in the air, but not actually touching it. It’s… agh, this is hard. Pattern recognition for a sense that doesn’t actually exist for a person who is atypical in that sense anyway?
That being said, while it wasn’t as important as the song of Gelel, in the Land of Hot Springs arc Jashin’s presence had a very distorted “sound” in comparison. SQ’s writing style for that chapter hAD a lOT oF thIS gOiNG on and the way Jashin communicated with Shikako directly was very much so “whispered / echoed / transmitted”. Even at the Fire Temple, I imagine the energy there was sort of humming or chanting–the monks harmonizing with the Temple.
Maybe that’s just how she interprets gods? If most people/things are a feeling to her, then maybe gods are a sound?
Sorry, I know this isn’t really about magical singing/songs, but this is just how I interpret the song of Gelel…