Thundercat, one of Kendrick Lamar's secret weapons on 'To Pimp a Butterfly,' emerges in time for Grammys

Those paying attention to the sound of contemporary Los Angeles as imagined by Kendrick Lamar's "To Pimp a Butterfly," nominated for an album of the year Grammy, might have noted a mysterious musician named Thundercat lurking in the background.

In late 2014 and 2015, he seemed to be everywhere....