Move over Sam Hunt; Carrie Underwood has a new duet partner for “Heartbeat.” Carrie recently posted an audio clip of her singing the chart-topping hit, with her 18-month-old son, Isaiah, joining in to make his musical debut. In the clip, Carrie begins singing the lines to the song and lets Isaiah jump in to adorably sing the word “Heartbeat.” Underwood captioned the audio clip by saying, “My sweet boy singing his little heart out. This is the most beautiful sound in the world!” https://www.instagram.com/p/BKNLXRSjGy3/