I Just Called To Say I Loved You by Stevie Wonder is in Gb at 112 beats per minute and runs 2:42 across 52 bars. It uses 21 chords — Db, C, Ebm, Dm, Ebm(maj7), Dm(maj7), Ebm7, Dm7, 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? I Just Called To Say I Loved You guitar melody tab.