"Hey, that's nice", "How's that going?" or something like it.
Also, no response is also a response, you could just listen to them. No one's going to say "I just started taking guitar lessons" and remain silent for the rest of the evening; for sure they have much more to say about it.
Why is it self-absorbed for someone to include themselves in the conversation, but it's not self-absorbed for you to come up to me and talk to me about your guitar playing?
You can come up to me and say, "Hey, guess what!? I just started playing guitar!" And I can't say, "No kidding? My mom just started playing guitar, too!" or, "No way! I just started drumming a few weeks ago. Maybe we can jam soon?"
How is my response "self-absorbed" but you starting a conversation about yourself isn't?
If you start the conversation, I'm just supposed to keep asking you questions about your experience until you're done talking about it?
I mean, if we're friends, shouldn't you care about what I think is relevant as much as I should care about what you think is relevant?
And anyway, if you _really_ want to talk about how it's going - can't you just take the conversation there?
I understand if you say something like, "Nice. I've always wanted to learn to play, and I never thought I could, and already I've learned so much, and I'm getting close to being able to play my favorite song."
And I say, "Oh, cool. Hopefully you can play my favorite song next. But it's really hard, you'll probably need a few years. You know, I used to be friends with Kurt Cobain's assistant, right? That's how I got into music in the first place....."
^ That seems self-absorbed. The first seems like genuine conversation.
I would say that in the best case we would take turns sharing about something personally important and being listened to and engaged with where we're at instead of quickly pulled off in another direction. For a bit anyway, before you get the ball.
I think the core of this question is generosity of time and attention, each person's ability to suspend their solipsism and engage with the other person as a person of equal importance to themselves. A good conversation is an act of intimacy.
We all want to be heard but no one ever seems to want to do the listening.
Also, no response is also a response, you could just listen to them. No one's going to say "I just started taking guitar lessons" and remain silent for the rest of the evening; for sure they have much more to say about it.