The evolution of a band can be either a progressive evolution or a regressive one.

While some bands are able to build on their past successes, others seem to lose the inspiration and revert to uninspired pop ballads or poorly executed concept albums.

The evolution of the Decemberists has most certainly been one of progression, innovation and execution.

In their latest album “The Hazards of Love,” the Decemberists skillfully weave between folky ballads and metal-based rock songs as they spin an elaborate tale of two lovers who encounter innumerable obstacles (including a malicious queen and three looming ghosts).

The 17 tracks offer a fully conceptualized and, at times, an absurdly twisted plot that mirrors an operetta.

Colin Meloy, the Decemberists frontman and primary artistic force, employs guest singers like My Morning Jacket’s Jim James and Lavender Diamond’s Becky Stark to take on the roles of his intricately conceptualized characters.

Amid a series of guest singers, an onslaught of instrumentals and the implementation of heavier guitar, the Decemberists make a definitive move toward change through an artistic fusion of fiction and music; an ambitious concoction even for a band of their standing.

In “The Hazards of Love,” the songs fit together like puzzle pieces of varying sizes.

While they are all ultimately different, they fit together almost seamlessly.

From the eerily supernatural ballad “Isn’t It a Lovely Night” to the percussion driven “The Wanting Comes in Waves,” Meloy illustrates his artistic wingspan while providing the listener with a cohesive concept album.

While the album can move slowly at times, Meloy’s expertly crafted lyrics offer the listener depth and profundity.

Meloy, once a creative writing major, composes lyrics with an almost Shakespearean voice. While some may critique his lyricism as precocious, his language is both beautiful and meaningful.

The last album delivered by the Decemberists, 2006’s “The Crane Wife,” introduced themes of literary proportions but fell short of concept album status. The critically acclaimed album also showcased Meloy’s lyrical savvy, but failed to employ the instrumental diversity that drives “Hazards of Love.”

In a strikingly heavier and stunningly darker approach to the orchestration and production, the Decemberists integrate a slew of strings, a powerful piano and some seriously rocky guitar. The change, while unexpected, fits the album perfectly, reinforcing its progressive rock foundations.

In addition to the indie-darling guest stars, the band also uses a children’s choir, adding to the “dark and mossy” feel of the album.

Even for some dedicated fans, this move toward heavier rock may be a bit disconcerting.

While compositionally and instrumentally successful, “The Hazards of Love” lacks the catchy hooks of past Decemberists songs like “July, July!” or “O, Valencia!”

Despite this sacrificial exclusion of the Decemberists’ pop sensibility, “Hazards of Love” is arguably one of the most well devised and effectively executed concept albums of the recent past.

In this dramatic evolution, the Decemberists not only remind fans why they are famous, but reaffirm that their creativity and inspiration are far from drying up.

So, when you put the record on for the first time, brace yourself. This isn’t easy listening and it’s most definitely not pop, but it’s a powerful testament to the talent of the Decemberists and an impressive display of their capacity as musicians and as storytellers.