Twitter is set to make a "big announcement" Thursday on Good Morning America, ABC's early-hour television show.

GMA teased the reveal on its Twitter feed Wednesday night.

Tomorrow on #GMA: @twitter will be making a BIG announcement... tune in! — Good Morning America (@GMA) April 18, 2013

So, what should viewers expect from the announcement? Online speculation points to the official launch of Twitter Music. A website for the service went live last week, hinting that a formal unveiling will soon take place.

Ryan Seacrest confirmed the existence of Twitter Music after posting a tweet that said he was playing with the app. It reportedly helps users discover new artists, and indicates which songs are trending among their friends and on Twitter at large.

It's not the first time that Twitter has eschewed press releases for television appearances to make big announcements. Last year, CEO Dick Costolo revealed a new look for Twitter's profile pages on NBC's Today show.

What do you think Twitter will announce on Good Morning America? Tell us in the comments, below.

Mashable composite. Image courtesy iStockphoto, mstay