Ugh; I hate situations like this, i.e., where someone's tone is so stinging. How well do you know this other musician, and out of curiosity, who asked you to make the announcement? It sounds like you didn't just take it upon yourself to announce the party, so it seems unfair that he directed his comment just to you. If that's worth emphasizing to him, then send him an email to that effect. Otherwise, just try to blow it off.