Wind and Anchor by The National Parks.

It's so open and well-separated that it's easy to pick an instrument and listen for the little details I know should be there--my favorite is the little boom of reverb from the mutes lifting off the piano strings. It has both male and female vocals (separate and together), acoustic guitar, violin, piano, light percussion. It's also just a gorgeous song. Maybe not the best bass test though.

Runner-ups go to Floya - Wonders and Rationale - Phenomenal.