A Shazam-esque opt-in feature coming to the iOS and Android status composer can activate your phone’s microphone, recognize a TV show you’re watching or song you’re listening to, and tag it in your News Feed post. Friends can then listen to a 30-second preview of songs or see a link to a TV show’s Page.

Facebook built the audio recognition feature from scratch over the last year and it will roll out to iOS and Android users in the U.S. over the coming weeks. It’s an extension of the feelings and activity sharing option rolled out last year that lives in the little emoticon icon in the status composer. Facebook says 5 billion posts have used the option to share what you’re feeling (excited, tired), doing (Drinking coffee, playing basketball), or what media you’re enjoying. Soon that last activity type will be much easier to share thanks to the audio ID since you won’t have to already know the name of the song or show, and won’t have to type it in.

If users don’t turn it on, nothing will change about their Facebook experience. But if they do, they’ll see a little audio levels indicator when they open the status composer that can identify any of millions of songs or TV shows on 160 channels (U.S.-only). The song or show will then appear in the list of activities you can choose from, and be added to a post with one click.

Thanks to APIs from Spotify, Rdio, and Deezer, users will be able to listen to 30-second audio previews of songs their friends share in-line in the Facebook News Feed. Licensing issues limit the ability to show video previews, so Facebook just displays the season and episode number, a thumbnail image, and a link to the show’s Facebook Page instead.

I tried the feature, and it was able to quickly identify popular songs, TV shows like Game Of Thrones, and even live TV like CNBC’s “Closing Bell” — sometimes in as little as six seconds. Facebook also says it can recognize live sports — a popular topic in social media feeds that could be even more prevalent now. One shortcoming is that Facebook’s song database is still limited and can’t ID more obscure tracks. It also can’t detect what you’re playing through your phone’s headphones, only what’s heard allowed, unless you’re using the default iPhone or Android audio player. So no tagging Spotify songs you’re silently jamming to on the bus.

The launch could spell trouble for audio ID heavyweights SoundHound and industry leader Shazam, which now has 90 million users and just raised $3 million more bringing it to $95 million in total funding. After people find out “what’s the name of this awesome song on the radio”, a common use case for these apps is sharing to social networks. Here, Facebook is cutting out the middleman and putting the feature in one of the most ubiquitous apps in the world. However, Shazam has an index of over 25 million songs, meaning it’s much more likely to be able to nail down exotic tracks.

If users turn on the feature and use it, audio ID could encourage more people to discuss music and TV on Facebook instead of elsewhere. Twitter has long reigned as the king of conversations about television and other current events, but Facebook has been on a quest to steal that crown. In the last year Facebook launched hashtags, verified profiles, and embeddable posts, plus it acquired public sports data filter SportStream and opened up new data visualization APIs for TV news and other media outlets.

This fight is partly about helping users connect around media, which can inspire passionate debate and engagement. But there’s also a lot of money to be made by being the digital watercooler. Facebook and Twitter both want to host the conversation because it provides them with monetizable data about what media people consume. It can then use that targeting data to coax big TV studios, movie producers, and record labels to buy ad campaigns.

While receiving the demo from the feature’s product manager Aryeh Selekman, I kept thinking “Wow, I bet Twitter wish it thought of this.” When I blurted it out, Selekman and the accompanying PR reps couldn’t help but let out a round of triumphant chuckles, though refused to comment.

If Twitter is serious about owning public discussion of media, adding some form of audio ID would be smart, whether through buying, building, or partnering. Perhaps Twitter should just buy Shazam. It might be expensive, though, which is the reason I said Twitter shouldn’t buy SoundCloud (and apparently the reason it passed on the deal). The rise of a common enemy in Facebook could catalyze at least a partnership between Twitter and Shazam.

“On the ads front, no one is able to target these posts directly today”, Selekman says. However, he admits “it’s definitely something we’ve thought about and will potentially do in the future.” For example, if you posted that you were listening to the new Beyoncé album, you could one day be targeted with ads for the singer’s new concert tour.

For now, though, Facebook will pass along tallies of how many times a song or show is tagged to its respective artist or studio. That includes matches that users decline to share. The data could help bands pick their next single or what song to pitch to TV commercials.

Audio ID is Facebook’s second new feature in a month that’s opt-in, showing a stronger commitment to privacy. The ability for Facebook to turn on your phone’s microphone is sure to stoke fears the company is wiretapping everyone. However, Facebook says it will only listen for songs and TV, not voices or other background noise, and none of the recordings will be stored.

On the brighter side are the new behaviors audio ID could unlock. Selekman tells me he’s getting married soon as is desperately trying to convince his future wife to make Michael Jackson’s “Rock With You” their first dance. He hopes that when guests inevitably go to take photos or videos of the special moment, they’ll use the Facebook audio ID to tag their posts with a little snippet of the song so people reading from the feed feel more like they were there.