A while back it emerged via a discussion of Donizetti’s Maria Stuarda that Leicester might have the “toreador!” aria from Carmen as his ringtone.
It seems to me that there is more that might be done with this idea.
For example. Leporello’s phone? It rings with “fin ch’han dal vino” but Don Giovanni bought him the phone and he’s not allowed to change the ringtone and he hates it.
The Marschallin: something subtle and beautiful that you’ve heard before, but you can never quite remember what it was.
Sesto: Toni Basil’s “Hey Mickey!” but only because Servilia was messing around with his phone and changed it and Sesto has been too preoccupied to switch it back.