Watch the Day 4 online guitar lesson by Ravi from Learn Guitar in 21 Days

We're still just going to play songs using the A and E chords, but now when you find a song that you know and sing the melody to yourself (or better yet, out loud, it keeps you honest and lets you hear yourself and improve your timing and musicality), try and add a little groove to it using the rock/blues rhythm.

In fact, you might even want to start with a one-chord song and incorporate the rhythm just to get the feel, then tackle some of the two-chord songs.