Caspian the sea is the largest isolated body of water on the planet; its semi-salty waters separate two historically significant and sometimes violent regions (the Russian federation and present-day Iran). Caspian the band crafts instrumental post-rock that conjures the always-salty, never-saccharine influence of recently significant acts like Mogwai, Sigur Rós and Explosions in the Sky. The Boston band's music sonically mimics waves of seaward isolation and calm, followed by complex and sometimes violent storms of echo-drenched (yet piercing) dual-guitar conversations. But Caspian is adept at navigating these sometimes choppy waters and in the end always seems to agree on a common destination. The epic "ASA," from 2007's The Four Trees, floats steadily on accordion drone and finally comes to rest on delicate and airy acoustic finger-picking.