I have a feeling that it's gonna be somewhat similar to the previous Cello lesson from....well, years ago.
Sophia holding the Cello (or maybe a Guitar this time, so nobody can say it's recycled content), Sam hugging her tightly from behind with a boner poking into her bum. Except this time he might be able to feel the fabric of her top while Sophia tries playing the Cello, being all flattered about Sam's boner trying to dig a hole through her yoga pants. She might even mention it, and Sam is gonna try playing it cool while drooling all over her shoulder as he's getting a good feel of Sophia's sideboob tightly wrapped into her top.
Ooooh the fabric...t-the fabric...aaahh...oooooh. Uhm...sorry, I got horny there for a second.
Or something like that.