Since art is by nature a solo endeavor, it’s the rare musical collaboration that doesn’t end in compromise. Yet Bolsa de Agua, the fifth and best album in the Gourds’ catalog, captures the Austin group locked in on practically every level. Half a decade has made survivors of the new kids on the block, yet they remain an oddball combination: deep-woods rootsy with an alternative art bent, led by hearty musical prowess and two songwriters who could not be more stylistically dissimilar. Kevin Russell is the meat-and-potatoes foot-stomping foundation of the group, whose best efforts resonate like charismatic old friends. The flipside is Jimmy Smith, whose work stubbornly refuses to yield to expectations. Like someone who asks, “You know what I think?” and then doesn’t tell you, his songs can frustrate until they creep into your consciousness and stay there. The newest Gourd, Uncle Tupelo-Wilco veteran Max Johnston, contributes two surprisingly earthy rock ballads that fit perfectly in the repertoire. These new recordings transcend the slapdash feel of the band’s earlier releases. And though any one of these songwriters could have made a fine album, together they’ve created what is surely one of the year’s best.