Complex sentence: In Spring 2004, Carbon Leaf signed with Vanguard Records, part of the Welk Music Group and in July of that year released their first album on a label, "Indian Summer".
Split into simpler sentences: In Spring 2004, Carbon Leaf signed with Vanguard Records, part of the Welk Music Group. July 2004 marked the release of their first album on a label, "Indian Summer".