IRyS got a collab with some rhythm game, they've done some Hololive collabs before too, I think:
I downloaded it.
Edit: It has a login campaign (free stuff), 'limited missions' (story stuff?), but also "Hololive collab song - Playable during 4/15 8:00 (UTC) ~ 5/5 7:59 (UTC)"
So there's a song! ....but it's only for a limited time...Edit 2: There are other Hololive collab songs in game, and you can buy them for what seems like a common in-game currency. So maybe whatever song is in this IRyS collab will be free to play for that time period, and then go 'on sale' afterwards? I don't know how this game usually does events, but seeing other old Holo collab songs gives me hope.