Turntable.fm is one of the more graphically-convincing group listening apps to emerge this month."

Before the advent of recording, music, by necessity, brought groups of people together to listen with the exception of the odd lonely troubadour or lovestruck serenade.

Once we could bottle the vibrating air otherwise known as sound, music became something we could summon up for private, on-demand listening — a phenomenon that grew more pronounced as MP3 players and then smartphones became capable of spinning private aural cocoons around us.

To torture this metaphor a bit further, those cocoons are now opening up, releasing music fans to flit about together like so many butterflies in a sunlit meadow. (Okay, we’ll stop with the cocoon thing already.)

Wahwah.fm's iPhone app, which we saw at SXSW, is set to debut in June, bringing group listening to the smartphone.

Due to a confluence of technological and social forces, the hottest thing going right now in digital music is the online listening room, which brings fans together to spin tunes for each other, chat about whatever’s playing, rate each others’ choices, and discover new music.

One of these new services, Turntable.fm (pictured above right), joins users in virtual listening rooms with DJ avatars on a “stage” and listener avatars in a “crowd.”

That web app duplicates the way club-goers listen to recorded music together in physical locations, but others, such as Outloud.fm and Listening Room, follow an online-derived format that mingles the group’s music choices with their chat messages in a scrolling activity stream that will look familiar to users of any general-purpose social network.

Meanwhile, the upcoming Wahwah.fm, inspired by the dual-jack Sony Walkman of yore, will bring this concept to the iPhone next month to let users listen together, chat, and find DJs based on location. Facebook and Spotify, meanwhile, are also said to be in talks to offer a similar on Facebook’s social network that would allow Spotify users to listen together.

So why is this happening in mid-2011, rather than, say, five years ago? First, social networks have not only conditioned us to being together online, but they’ve given us handy portable identities that can be plugged into these listening rooms, most of which require a Twitter or Facebook handle for entry. Second, recent advances in browser and mobile app technology have made it possible to sync everyone up to the same song at the same time, regardless of our respective locations.

Outloud.fm lets anyone in a room play a song by dragging and dropping an MP3, M4A or WMA onto a pane to the left of the activity stream.

“Things change so fast in software that even just five years ago, this would have been considerably tougher to pull off,” said Outloud.fm developer Mike O’Brien. “Browsers are getting more powerful by leaps and bounds, and some truly amazing and brilliant open source projects (like node.js, Redis, and Soundmanager2, which we rely on heavily) have emerged, making these kinds of applications much more tractable. Developers have so many more great tools at their disposal that just didn’t exist then, and we can iterate more quickly on new features than ever before.”

This concept has already taken a variety of permutations (mobile app, web app, or Facebook app), but regardless of how things are set up, all of these new apps unite listeners around a series of songs in common, proving once again that technology doesn’t necessarily “want” anything — like for us to be alone — but that it can be bent to our will, whatever that may be. If we want to listen together, now, we can, even if we’re online.

• Facebook/Spotify (unlaunched; read about it)
• Listening Room (read about it)
• Outloud.fm (read about it)
• Turntable.fm (read about it)
• Wahwah.fm (unlaunched; read about it)