When it comes to my singing, I've got a couple of fans. My son and daughter don't mind that my vocals are off tune [1], in fact, my tunes help them sleep. If your tot has trouble transitioning from bathtub to bedtime, try breaking out in song. Turn this into a fun activity by having them help you with the lyrics. Once you perfect the tune specific to the child, sing or hum it to soothe them.
Source [2]