After their comeback reunion in 2008, Los Fabulosos Cadillacs have been touring intermittently and even released a couple of records, comprised mostly of reworkings of old songs.

A proper studio album seemed out of the question since their last one dated from 1999 and yet, 17 years later, the band surprised all disbelievers with La Salvación de Solo y Juan.

If the mere existence of this album is already startling, its contents are even more so.

Should anyone have suggested back in the mid-'80s, when the Cadillacs were little more than a gang of wannabe rude boys with more attitude than chops, that 30 years later they would be making a concept album heavily indebted to '70s classic rock (and '70s Argentinian rock in particular), the band's reaction would probably had been to spit in the eye of the imprudent defamer.

As most young brash acts trying to make a name, in their beginnings, the Cadillacs were very vocal in their contempt for their predecessors and competitors.

Many decades later, however, one suspects that as teenagers they were listening to a lot of other stuff before turning to the Specials and the Clash.

Bands making records again after a long hiatus are faced with an unenviable dilemma: should they turn backward to what made them famous in the first place, or forward in an attempt to sound different or contemporary? The Cadillacs dodge the issue by looking to the past, yes, but to a past that pre-dates the history of the band.

La Salvación de Solo y Juan is a bona fide rock opera with echoes of Quadrophenia and Tommy, but most of all of Argentine bands such as La Máquina de Hacer Pájaros or Vox Dei, and even the folksier Por-Sui-Gieco or Arco Iris.

None of these groups can be said to have remotely influenced the trademark Cadillacs sound, so in that sense, La Salvación de Solo y Juan represents a bold stylistic departure.

Of course several songs still feature their characteristic Caribbean/Latin spine of horns, bass, and percussion (most noticeably standout single "La Tormenta," whose bass tapping directly references their 1995 hit "Mal Bicho"), but this is largely a guitar album -- the first ever for the band.

Acoustic guitars, rarely heard in their discography, are predominant here, as well as somber instrumental passages, organ parts, and electric guitar solos.

Ironically, while this may be new for the Cadillacs, it makes their music less distinctive -- after all, there are many more guitar-based rock bands than horns-based ones.

The concept story, a depressing tale of two brothers' troubled upbringing under a stern father, was written by bassist and co-leader Flavio Cianciarulo and Mexican writer Adolfo Vergara Trujillo.

A bit of a meandering cliché, it is arguably the album's Achilles heel.

The songs, however, do not so much tell the whole story (which can only be comprehended by reading the text included) as comment on it, and therefore can generally be appreciated on their own terms.

These are by no means negligible: the Cadillacs have long grown into accomplished musicians and arrangers, and the entire vision is perfectly realized.

This is also where the album's true value lies.

Far from delivering a by-the-numbers, lackadaisical offering, the Cadillacs have clearly invested a lot of thought and effort into the making of this record, possibly the most ambitious of their entire career.

Instead of playing it safe by re-creating their old hits, they chose to bring a labor of love to completion -- they had been considering this project since the mid-'90s -- a valiant decision that can only be commended.

La Salvación de Solo y Juan won Best Rock Album and Best Rock Song (for "La Tormenta") at the 2016 Latin Grammys.