Changing from era is unique. Changing from century is extraordinary. Changing from millennium is something that not many people can say they’ve done that. People who have gone from 1999 to 2000 can say they have been part of an historical event. It will take many generations before it happens again.
Same as an era changes in which music changed with them through the ages, so did it undergo extraordinary changes when transforming to the nillies. With technology expanding it’s horizon, so there became more space for music to go to. From MP3 players, who had just been born, to the solution to have all the music in the world with you, every time, every where: Music Streaming.
Changing from a one millennium to another brings changes with him in all it’s forms.