Belgium is well known for its sumptious chocolate goodies, artisan beers and as the HQ of the EU, but not their music. Indie-rockers Balthazar aim to change all that. Named as if the band were a Transylvanian count, the band released an immensely successful and well-received debut Applause in 2010. It showcased quirky, youthful servings of tongue-in-cheek indie, with fans and critics revelling in the upbeat attitude. A lot of that carefree nature has been lost on second full-length effort Rats, the group instead offering a mature edge with instrumental experimentation and meatier subject matter.

'Sinking Ship' is a laissez-faire lump of smooth, jazzy drums and soft guitars. The dynamics are masterfully toyed with, meaning that volume becomes an integral part of the song – almost like an extra instrument, bending the sound on a whim. The song shimmers, but perhaps the most notable aspect is how much lead vocalist Martin Devoldere manages to pull off a Bob Dylan impression. 'Later' is a night-time cut, with flowing strings and muted bass bumps. It's a meandering escapade into edgy midnight semi-ambience; there's tension and an overarching sense of 'car-chasedness'. 'Any Suggestion' decelerates the pace, featuring dead-weight drum beats, organ drones and howling vocals. It's an off-kilter cut, and Devoldere sounds like he's singing "Anaesthetist and, anaesthetist and," when he's actually saying "Any Suggestions? Any Suggestions?" Pizzicato strings and all manner of orchestral percussion get a look-see into the macabre tango, making for a decisively intriguing cut.

Balthazar have made a subversive indie LP in Rats, using a multitude of elements from Western classical music, especially in the instrumentation, demonstrated by their lack of reluctance in making use of brass and strings. It has lost a certain naivete, which isn't inherently bad, but those who fell in love with their first-album-sound may be left feeling disappointed. The kangaroo basslines mostly remain, and the blatant knack for words still rears its glorious face. It is more lethargic, however. Those stoic few braying for more of album number one might not be satisfied, but those that stick it out will be greatly rewarded with a rich, deep album full of twists and explorable noises.

'Do Not Claim Them Anymore' is a hurried bass-led finger-snapper with maudlin lyrics about love: "Hold me close my dear, there's nothing wrong with some twisted fear." It's sparse and hazy, with an intensely melodic chorus and glistening synths. It's sweet, with a bitter aftertaste – twee-noir. 'The Oldest Of Sisters' is entombed in a chilling, brittle ribcage of dry guitars. When the chorus lifts off, the heart of the track beats once more; haunting brass notes and jailbird backing vocals underpin a powerful delivery from Devoldere. 'The Man Who Owns The Place' struts with a sensual '60s Bond-style danger – it's dark and loungey and faintly evil. The strings have an expanded role here, creating visible tension alongside the gruff, gritty growlings.

Rats is a strong record. There are many delightful fragments of inspirational music and plenty of juicy cuts to sink your teeth into. The band have made a concerted effort to grow up, and although that means changing fairly drastically, it paid off. Bands do change between records anyway, evolution is key to consistently good music – if artists stayed the same, people would get turned off faster than you can say 'Jodie Marsh'. Sometimes the gamble doesn't pay off, á la Delphic, but fortunately for this band of Belgium troubadours, it has.