Varda the Message

I've put some thought into this myself. Although I'm not sure if it's at all what Haynes intended, when I watch this scene I consider that everyone in that studio, not just Curt, is fucked up (to use the technical term! ;) ) on something. And different drugs affect one's perspective differently; someone on quaaludes or smack is NOT going to hear/see/feel the same way as someone on coke or speed. The sensations will be different and they won't agree on what's actually happening. My guess is that there are two different highs going on on either side of the studio glass, and Curt isn't dosing on the production team's stash.

Cocaine looms large as a force for Brian to reckon with later in the movie, and we already know that Curt has a weakness for heroin. These two drugs have opposite affects on the body; to greatly simplify, coke's an upper and smack is a downer. Both drugs affect the nervous system & the brain, thereby affecting perspective and sensation. If – as I suspect – Brian is on coke during this scene, he will be more susceptible to Jerry's manipulative needling & snide remarks and more likely to act on them impulsively without thinking. Brian also won't be on Curt's "wavelength", and thereby not picking up on his musical nuances (which is crucial for a producer/musician relationship so as not to "waste tape"). Brian and Jerry are so caught up in sorting out their public-face pecking order, they're not even listening to Curt.

(Note that, as the manager, one of Jerry's manifold responsibilities is to ensure that the "proper creative atmosphere" is provided...in other words, part of his job is to keep the drugs free-flowing. Whatever Brian and Curt are snorting, shooting, licking or smoking, it's almost 100% likely that Jerry procured it for them. So his machinations may run deeper than just bitchy comments. If he feels Curt is a threat to his control of Brian, and he wants Curt out, he can ensure that Curt & Brian don't see eye-to eye by various means, only one of which can be the fostering of completely different drug habits for each artist.)

Just my 2¢, gleaned from past music industry experiences. Like I said, that may not be Haynes' take on it at all.