Can I manually adjust or change the duration or length of each clip?

Our music video creation software can help you make great videos quickly and inexpensively, though it is not a traditional video editor. 

At the moment you have 3 steps with Rotor...

1) upload a music track of your choice (in .mp3, .wav, .ogg, .aac format) 
2) choose your video clips (we have around 1 Million clips to choose from! or if you prefer, you can even upload your own clips) 
3) lastly, you select the style of music video you would like. This will set the overall look and feel of the video.

Hit preview, and your video will render. Piece of cake

However, there is currently no way to align certain clips with specific parts of your song (or a way to manually adjust the length of individual clips), our apologies! Though this is something we are working on

I hope this helps a little to explain some of the possibilities as well as the limitations.