Sending babies and their hip parents off to a restful slumber since 2006, Rockabye Baby! is a popular series that issues collections of instrumental lullaby versions of songs by well-known artists. Kicking off with inaugural sets of Coldplay, Metallica, and Radiohead songs, Rockabye Baby! went on to cover artists ranging from the Beatles and Bob Marley to Björk before the end of the decade. Highlighting their gentle arrangements, often featuring keyboard and bell-type tones, the series' first compilation, Good Day, Goodnight, appeared in 2011. Releasing upwards of a half-dozen...