After leaving Milwaukee for Boston in the mid-’90s, Peter Mulvey earned spare change playing in subways and on the streets. With Notes From Elsewhere, he’s in full busker mode, accompanying himself on his own crowd-pleasing songs with only acoustic guitar. Perhaps the softer environs of a bookstore or coffeehouse might be the best setting for his melodic, lyrical material, telling stories about relationships, growing older, relationships and, well, the passage of time.