[Endless, Nameless] I'm really struggling, please help!

I’m playing Endless, Nameless at the moment and I’ve reached a point I can’t seem to progress past I can’t get the sonori spell to work upon returning to the cottage, please could someone hint at how to use it exactly? I can hear the singing, have listened to it; I assume I have to cast the spell at a specific point? Does the stone need to be activated? If so, how?
Thanks so much in advance!

What game are you playing?

endless, nameless; can’t believe I omitted that!

OK! I edited it into the topic title to help people find it. Unfortunately I didn’t get that far in the game so I can’t actually help!

You’re most likely trying too early. Have you crossed the labyrinth? You can’t get in the first time you meet her.

In case you need help completing the spoiler ed task, it is very complex. The ‘other players’ in tbe hotel can be helpful, but I can give you more hints if necessary.