I don't understand the confusion over creating a complete track with EZKeys! It really is pretty simple. Just drag a groove you like for intro into the timeline and adjust chords to your liking. Then drag a groove for verses, choruses and bridge until you've built your entire track. EZ to change key, tempo, chords and length of any section.
Can you post a song you've done that is mainly piano and vocal?
Just saying "That's easy!" doesn't really prove anything.