It was a slow, patient and meticulous artistic evolvement that led the American duo Calexico to the fullness of its appealing Tex-Mex sound that has delighted growing audiences, particularly in Europe, in recent years. The act, based on the core duo of multi-instrumentalist Joey Burns and drummer John Convertino, has enjoyed snowballing popularity since the release of its second album, 1998’s «Black Light,» which shaped relatively unfocused earlier ideas into a more cohesive form. The album’s remarkable exposure, considering its independent release, and uncommon crossover appeal to various tastes, suddenly made the unassuming Arizona-based act a hot touring prospect circa 1999. The group, which has since toured here on three occasions, appearing at bigger venues each time, will be returning to Greece this week for three shows in Athens, Thessaloniki and Larissa. Burns and Convertino will be bringing with them a sizable entourage of players to capture the sprawling qualities of their adventurous cinematic sound on stage. Parts of the show may well ignite into a full-on Mexican fiesta, complete with mariachi horns, as was the case during one of the band’s previous performances here two summers ago. But a great deal of this group’s charm also entails its ability to capture both sides of the emotional story. The ebullience of some material is countered by contemplative introspection elsewhere. The duo’s expressive songwriting gamut touches on various styles, including rock, country, jazz, and Portuguese fado, in elusive yet admirable fashion. Calexico are touring on the strength of a worthy new album released last month, «Feast of Wire,» the duo’s fourth. Again, a tantalizing array of sounds feature, perhaps in the group’s most refined and cohesive work to date. Burns and Convertino began working together as far back as 1990. They first gelled as the bass-and-drums rhythm section in an experimental rock group, Giant Sand, led by Howe Gelb. The pair also worked with other obscure yet interesting acts, including Friends of Dean Martinez, Barbara Manning, and Lisa Germano, before deciding to experiment alone with a growing collection of old instruments purchased from a second-hand store in Tucson, Arizona, Calexico’s home base. That was 1996, the year the group released its debut album «Spoke,» a home-recorded effort with vague hints of what lay in store. Thursday: Athens (Ark Nr. 6, 18 Themidos, Tavros, tel 210.338.8400); Friday: Larissa (Mylos); Saturday: Thessaloniki (Mylos, 56 Andreou Georgiou, tel 2310.551.838).