ESA astronaut Tim Peakes message to the children who took part in the 2016 Astro Pi coding challenges to hack his Astro Pi mini-computer, on the International Space Station, into an MP3 player.
The music heard is called Run to the Stars composed by one of the teams who took part in the competition.
More about the MP3 player coding challenge: https://astro-pi.org/coding-challenges/mp3-winners/
More about the Sonic Pi challenge: https://astro-pi.org/coding-challenges/sonic-pi-winners/
More about Sonic Pi: http://sonic-pi.net/
More about Astro Pi: https://astro-pi.org/about/mission/