I could have chosen any number of Orbital tracks, but I started with this one because this song has penetrated pop culture so deeply. It is the theme track from Hackers, and has also been featured in CKY2K, Mortal Kombat, and Mean Girls.
Orbital is a British duo consisting of two brothers, Phil and Paul Hartnoll. Halcyon is a reference to Halcion, a tranquilizer to which the Hartnoll’s mother was addicted. The original mix of Halcyon is a longer and more downbeat version, and was dedicated to the Hartnoll’s mother. The vocals are a “backmasked vocal sample by Kirsty Hawkshaw from “It’s a Fine Day” by Opus III” (Wikipedia).