Glen Hansard has always been willing to follow his muse wherever it leads. But it’s never taken him anywhere quite this wild before. For his fourth solo album, the frontman of The Frames and Swell Season — not to mention the Tony and Oscar-winning songwriter of Once — revamps his sound more drastically than at any other point in his career. Almost as impressively, he does so without sacrificing the core qualities that have defined his sound and style for decades. On the hour-long This Wild Willing, heartrendingly beautiful acoustic balladry remains the Irish troubadour’s stock-in-trade. But while a gently plucked acoustic guitar has often been enough for him in years gone by, it’s just the starting point for these dozen dynamic songs. Aided by producer Dave Odlum and a cast that includes Once partner Markéta Irglová, Irish electronic musicians Deasy and Dunk Murphy and assorted Iranian musicians and vocalists, Hansard opens the sonic and stylistic floodgates and lets waves of post-rock textures and effects wash over the tracks. Some are subtly fleshed out into darkly textured jazz-folk grooves flecked with horns. Others become vaguely unsettling works whose beauty is offset by ominously droning tones. Still others gradually swell until they explode in mammoth sonic squalls reminiscent of Sigur Ros. But the more his musical landscape broadens, the more Hansard’s vocal delivery narrows, with many of these songs being presented in a hushed whisper or a hazy croon. All told, it makes This Wild Willing his riskiest and most inventive outing in years. Not bad for a guy who could just as easily rest on his considerable laurels and churn out Once sequels ad nauseam instead of restlessly chasing the sounds he hears in his head. And if he’s willing to go the distance, so should you.