it worked well with the clip because the clip was based on animated fights i then had to delete part of the track and the i went onto track and clicked fade out.
when i had done this it brought a purple line at the bottom so this allowed me to change when it faded out and how long the fad was going on for.
i found this easy to do as the teacher showed us with the clip i then used the purple line bar which was the fade out bar to make it dimmer more.
Here is a video that i put into garageband i also added the kung fu fighting track which plays throughout the animated footage.