French company Musinaut wants to make the music you listen to change according to your mood. To achieve this, they have invented a special player capable of reading your brain waves, interpreting them, and then mixing the music to match your state of mind. So if I was using one right now, I would be listening to a funk version of Abba's Dancing Queen. Sadly, the key for this feat is a new format called MXP4, which may limit its adoption in the music industry. MXP4 has several mixes of the same song built in, recorded by the artist. When the player detects a mood variation, the music changes accordingly to fit it. According to the company, this makes the song some kind of living creature, with endless variations to match your mind. I would have been happy with the same technology applied to current players, mixing existing songs automatically as the mood changes—although often I use music to change mood, rather than match it. What about you? Do you think this automatic DJ playing is useful? [Musinaut]