There are at least three bands/performers who go by the name Callaghan. 1. Callaghan http://www.callaghansongs.com is a British acoustic/pop singer, originally from Lincolnshire and now performing in London and Nashville.
Born in Boston, Lincolnshire to a musical family, Callaghan was classically trained on flute from age 6, then gravitated toward singing and playing piano. By 14 she was writing songs, and started trekking to London to record with various producers.