Currently I am working on a song that has a very calm section and proceeds to a section with drums, a synthesized pluck, an eletric bass, guitars  and of course, a set of chords with a very simple melody. But it still feels empty. :/ I tried playing the same chords and melody in a different synth but it sounds weird with above the piano.

The best songs I can give as reference to what I want to do are Summertime by My Chemical Romance https://www.youtube.com/watch?v=ITIPYRcKbKI and 26 by Saints of Valory https://www.youtube.com/watch?v=1qY3lPdn-Mk

Any ideas? Thanks guys!