Mamma Knows Best by Jessie J is in Am at 150 beats per minute and runs 3:14 across 52 bars. It uses 16 chords — Bb5, A5, D, Am, Bb7, Bb, N.C., Am7, and a few more. The chord diagram changes as the song plays and the words light up as they are sung, so you can strum and sing along without reading ahead.
Want the melody line note by note? Mamma Knows Best guitar melody tab.