16 of the biggest hits of the year in piano/vocal/guitar arrangements, including: All of Me (John Legend) / Best Day of My Life (American Authors) / Dark Horse (Katy Perry) / Fancy (Iggy Azalea) / Happy (Pharrell Williams) / Let It Go (Idina Menzel) / Pompeii (Bastille) / Problem (Ariana Grande) / Raging Fire (Phillip Phillips) / Timber (Pitbull featuring Ke$ha) / and more.