In 2015, a small company called AmpMe rolled out an app with a clever premise — it let you sync audio playback across any number of phones, offering users a (hopefully) better option for filling a room with music than just placing a phone in a bowl. Today the company is taking the idea a step further with an update to the app that extends AmpMe to Bluetooth speakers.

The basic workings remain the same. Everyone still needs to use the AmpMe app — which is free and available on iOS or Android. One person acts as the “host,” and they can play music from SoundCloud, YouTube, or their own local library. AmpMe uses high-frequency sounds to sync all the devices together, and rom there, there’s no upper limit on the amount of speakers or phones you can loop together. The only limit is that you can only connect one speaker to each phone.

I was impressed with the idea when I originally got a demo from CEO Martin-Luc Archambault in 2015, even if the syncing wasn’t totally perfect. Archambault recently came back to The Verge’s office to offer a quick demo of the new Bluetooth speaker functionality, and the idea now feels fully formed. The beauty is that AmpMe is basically device agnostic — you can use just about any phone, and just about any Bluetooth speaker. (Archambault says his team bought the top 100 speakers on Amazon and tested them all.)

The AmpMe team has also found a clever way to fix those slight delays in the syncing. If your phone or speaker is lagging behind (or running ahead of) the others, you just adjust a slider in the app. The app will even learn how much delay your phone is dealing with over time so that you don’t always have to make those adjustments.

AmpMe will remain free for the foreseeable future, but at some point a company has to make money. Archambault says that is likely to show up in the form of ads, maybe something along the lines of what you deal with on Spotify.

Eventually having to suffer through that might still wind up being worth it. AmpMe addresses a very specific problem, but it solves that problem in a really smart way. And the recent addition of YouTube support — AmpMe only worked with SoundCloud at launch — adds a new layer to the experience, because the app syncs the video playback across devices as well. It’s the kind of feature that feels like it could be very valuable for AmpMe if the idea of just being a party music app doesn’t pan out.

Update December 15th, 11:42AM ET: AmpMe automatically syncs phones, and no longer uses a 4-digit code to do so. This story has been updated to reflect that.