DEAR PRUDENCE

Dear Prudence: My best friend and I recently celebrated our birthday together.

Both of us were very adamant that we wanted a specific, niche genre of music playing (think sea shanties) in keeping with the theme of the event.

But my friend’s partner kept turning down the music, requesting to change the playlist, and even just going and turning on other music.

Am I right in thinking this kind of controlling behavior is a total red flag?

How can I convince my friend to see the problem here?

— Party Pooper

Dear Party Pooper: Well, you know what they always say: When the stereo is playing sea shanties, you shan’t turn them off. And your friend’s partner did it anyway!

This is more than a red flag; it’s a pirate flag. Your friend’s partner commandeered the aux cord, a party foul and an affront to maritime law.

Maybe they thought it was one of those free-for-all parties where one can play what they want. But as a secondary invitee, that feels mighty audacious.

It’s unclear from your letter whether you’ve already tried to talk to your friend and they didn’t want to hear it or if you’re planning on talking to your friend and are looking for language. Let’s say it’s the latter.

Having a one-on-one conversation, or a two-on-one if your best friend wants to join, away from the partner is the best way to go here.

Start with how the behavior affected you. It was your party, you set an intention and he repeatedly insisted on doing whatever he wanted.

Your friend may say it’s no big deal, he’s just a fun guy, he’s a DJ. OK, great. Good for him. The point is you had a party for yourselves, and you felt his behavior was inappropriate and controlling.

This can segue into your concerns about your friend’s relationship. Ask her if he’s always like this, if she sees it as an issue at all.

Right now, it seems important to figure out what your friend thinks about her boyfriend and how she views her relationship.

From there you can have the conversation about whether they should stay together.

Slate’s R. Eric Thomas is filling in as Dear Prudence while Jenée Desmond-Harris is on parental leave. Submit questions at slate.com/prudie. Got a burning question? Thomas will be online to chat with readers every Monday at 9 a.m. Send him your questions and comments before or during the live discussion.