First of all. You need headphones.
Then for the first level you listen to see what side you hear stuff on, and you move towards it. When the sound is centered you should scoop up the next instrument. Don't worry about missing. You get infinite tries. After picking up an instrument, you have to pick up another.
AT THE VERY END. THE MUSIC WILL GO QUIET. AND YOU WILL HAVE A CHOICE BETWEEN 2 SOUNDS!!! THE SOUND YOU PICK DETERMINES THE NEXT LEVEL!!!
For "street style" levels you got to avoid the invisible cars heading towards you by avoiding their horns. If you only hear their horns on one side of your headphones, they missed you. On chase levels you got to chase a person while avoiding the oncoming traffic, hit a to accelerate.
I hope this helped.