Music has always affected the listener's mood. Now, a Japanese company has built a headphone that plays music according to your mood.

Japanese company Neurowear developed a pair of headphones, called Mico, with an electroencephalography-enabled sensor. The sensor is able to read brain waves and with an iPhone app, plays music suited to your mood.

The headphones look pretty normal but have an Electroencephalography (EEG) reader that rests on the forehead and senses neural activity. It exhibits what mood the wearer is in through an LED display on the earpieces. A sensor sits squarely on the forehead to measure brain waves. It then works with the Mico headphones to play songs in a music library. Currently, the 100 tracks in the library are tagged with one of three moods - focused, sleepy and stressed.

A prototype of the headphones were shown at South by SouthWest.

Neurowear is known for its unusual product line that includes wearable cat ears that also respond to mood. Many of its products center on controlling gadgets with the wearer's mood or mind.

The cat ears, called Necomimi (Japanese for "cat ears"), are a pair of plush-covered cat ears that can perk up when you are happy, droop when relaxed or sleep and twitch or wiggle.  A similar EEG reader detects mood. It's one of the best-selling products by Neurowear and in the furry accessory market.

If the wearer wants to change the mood suddenly, the phone just needs a shake and it will clean the musical slate. The headphones can also play songs at random or suggest new songs when it senses a change in mood. This helps users find new songs.

The headphones are still in the early prototype stage and the company hasn't announced when it will be available on the market.