There’s instant popularity, which is often a hollow, hyped-up and short-lived form of excitement, and, at the other extreme, the snail-paced development from obscurity to wider acceptance, a course often associated with people genuinely attached to their line of work rather than the prospective material benefits it could generate. Musician Thanassis Papaconstantinou, nowadays quite a hit on the local circuit following years of peripheral hibernation, qualifies for the latter category, it would be perfectly safe to say. Consider his approach and progress along a far-from-the-spotlight course. Papaconstantinou, a self-taught musician, spent years penning telling songs, at once musically simple and articulate, from his off-center hometown of Larissa, northern Greece, as a passionate side activity to a full-time job as a state-employed mechanical engineer. The albums, consistently commendable, emerged at a steady rate, beginning in 1993, but it took several years and albums before the number of fans began to swell to any noticeable degree. Not too far back, as recently as three or four years ago, Papaconstantinou, a seemingly reluctant public figure, was still performing to modest crowds – very rarely, too. The number of fans, frequency of shows, and onstage confidence level have all since risen, and Papaconstantinou, now in his early 40s, has apparently retired prematurely from his regular daytime job to focus on his music efforts. Highlighting this impressive rise, one generated mostly by word-of-mouth publicity – and, it should also be noted, sturdy support from the popular and admirable songsmith Socrates Malamas, who regularly performs songs by Papaconstantinou at his own shows – the musician will play his biggest show yet this Sunday night at the open-air Lycabettus Theater. Joining Papaconstantinou will be his regular backing band of recent years, an adventurous and spirited lot of players that have reworked some of the songwriter’s older material and added a more abstract, improvisational flair to newer work. The lineup includes winds player Floros Floridis, a leading jazz experimentalist on an international scale and longtime member of the cult rebetika surrealists Heimerini Kolymvites, as well as a long-serving brass band, Banda Tis Florinas, Giorgos «Baduk» Apostolakis, a riveting electric guitarist who has spent years working with Blues Wire, a top-notch Thessaloniki-based blues act, and, also on electric guitar, Babis Papadopoulos, who spent years working with the top-selling, now-defunct, Thessaloniki rock band Trypes. Papadopoulos, who first joined ranks with Papaconstantinou for his «Vrachnos Profytis» album in 2000, brought along his former band’s apparatus of electric guitars and their coarse and dirty sounds as a new addition to Papaconstantinou’s previously acoustic-dominated work. The guitarist also brought along former bandmate Yiannis Angelakas, frontman of Trypes, who provided the vocals on several tracks on the «Vrachnos Profytis» album, which eventually was hailed as that year’s best release by respected local critics. Angelakas will appear as a guest at Sunday’s show. The relatively recent rock-inflected approach to Papaconstantinou’s peculiarly constructed old-school Greek material has helped attract a mass of younger listeners. On its follow-up, «Agrypnia,» released two years ago, Papaconstantinou drifted even further from his early period’s pristine approach for his most wayward album to date. The album’s reduced emphasis on rigid song structure for a less disciplined, wayward musical adventure, inflected with jazz and rock elements, highlighted the artist’s willingness to evolve. Right after that album’s release, Papaconstantinou, at the time still relatively unknown on a festival-circuit scale, was called up for his biggest ever engagement as a stage performer, an appearance at a Womad festival in Athens before an audience of thousands as part of a bill that included international acts such as David Byrne and Cesaria Evora. The choice was surprising yet deserved and seemed like a huge leap for the stage-shy artist. Considering that occasion, and the growing legion of fans since, Sunday’s Lycabettus Theater booking could go down as an almost predictable development in Papaconstantinou’s fascinating career. Tickets are on sale at Ticket House in Athens (42 Panepistimiou, tel 210.360. 8366) and Thessaloniki (20 Ethnikis Amynis & Tsimiski, tel 2310.253.630).