It is not.

Next test: repeatability. Can she get the same incantation from the same rock recorded identically on multiple other rocks?

If she draws out the whole huge diagram for each one, sure, she can make several different rocks say the incantation used on the glowrock.

She only does it for three total before disenchanting all of them; even duplicating and tracing gets exhausting pretty fast. Once she's established that one enchanted artifact can have its incantations read repeatedly, she swaps in the Tikbalang medallion and gets the first incantation used on it instead. Time for the moment of truth: how utterly alien and unrecognizable is it?

Well, it's definitely not a language she recognizes. It's a woman's voice, creaky and precise and bored-sounding.

Okay, that's definitely a human language with sounds her mouth is capable of making, which was not guaranteed and deserves appreciation. She also appreciates the precise pronunciation, though that's entirely expected--if she can't get this translated, one possible (terrifying) last resort is to memorize the recording and reproduce it sound-for-sound without knowing what it means. But that's a worry for later. For now, she puts that rock away in a carefully labeled bag and attempts to put the second incantation ever used on the medallion onto a different rock by the same process. There were four diagrams used on it, but she's prepared to find three, or five, or twenty-seven incantations. 

More incantations, all by the same lady. Seven in all.

Her email to Bella reads:

I got the incantations from the Tikbalang medallion. I can't send you sound files because I still haven't figured out how to get magic sound to cooperate with computers, but I'm going to try to make phonetic transcriptions next and you'll be welcome to look if you're curious. The weird thing is that it had seven incantations and only four diagrams, so either there's some ambiguity in the definition of a spell diagram such that I didn't get all of them, or there's some way to do runecasting other than "one diagram and one incantation at a time". Or something else weird is going on.

Do you think it'd transmit over the phone? I don't have any particular talent at identifying languages but it might be useful.

Somebody could have just wanted the same meanings for more than one incantation. Maybe the incantations were long enough it was safer to split them into chunks.

If they used the same diagram twice, my diagram-printing spell should have gotten it twice; that's how it worked when I tested it on a rock I had enchanted and disenchanted repeatedly with the same diagrams, anyway. Maybe if it was the same one consecutively it would only show up once. I'll make a note to test that. 

I definitely want to see if it works over the phone. My number is [a number]. Call me whenever works for you; my parents are fully informed now so pretty much all afternoons and evenings are fine.

Bella calls after school the next day.

Margaret is expecting a call and therefore is the one to answer the phone. Once the initial hellos are out of the way, she says, "Okay, here goes", holds the phone up to the rock labeled "Tikbalang Medallion 1: Do Not Overwrite" and gives it a tap.

"Yeah, I don't recognize that. But I do hear it."

"So phones work but computer recordings don't. That's so weird."

"Yeah. I mean, phones don't work by recording the sound and playing it back, the delay would be noticeable if they did."

"Sure, but my previous hypothesis was that the sound was purely illusory with no actual vibrations in the air. Oh, wait, if that was the case it wouldn't be affected by plugging my ears, one second--" she sticks her fingers in her ears and hits the rock again with an elbow.

This affects how she hears the rock as though the rock were making normal sound.

"Okay, not illusory unless the illusion can tell when I stick my fingers in my ears, it's some kind of sound waves that hate microphones or something. I'm so confused."

"It could be non-sound-waves that just imitate the behavior of normal sound with respect to most objects, like whatever you stuck in your ears."

"Being waves of something other than sound is a possibility I guess, but it doesn't explain why they interact one way with my eardrums and another way with the part of a microphone that responds to sound waves. Maybe I should get one of those speaker horns sports announcers use, and a plastic cone, and see if they amplify like normal sound waves in either case."

"I don't know if it's waves in particular, just that it's something that muffles normally. I mean, if it didn't, you'd be able to hear it all around the world, yeah?"

"It could in theory have been something that dissipates with distance without being muffled, or be a totally mental phenomenon, but yes. Hmm, what other experiments could I do besides amplification? Maybe start with a sound that makes something resonate, and see if a magic recording does the same . . ." (She's taking notes on all of this.)

"Resonate? Like... breaks glass, or d'you mean something else? I don't know a lot about sound."

"Breaking glass with sound is the phenomenon I mean, yeah, but there are other things that do it without breaking. I think tuning forks are optimized for that? Not that any of this is as important as finding a linguist."

"I'm not sure how you find a critter linguist."