You could count on a couple of fingers the number of bands that might weigh the question: "Which rock opera should we do?"

The Who not only banged out two of them, but anyone compiling a list of the Greatest Rock Operas of All Time would be hard-pressed not to have in the Top 10 both "Tommy" and "Quadrophenia," the focus of the current Who tour, which stops at Target Center Tuesday.

"Quadrophenia" was released 39 years ago, so there is no anniversary associated, and it hasn't been in storage that long, as it was the centerpiece of the band's 1996-97 tour.

Why "Quadrophenia" now? "We've been trying to find something we can do together, Roger and I," Pete Townshend said in a teleconference with the band's only other surviving member, singer Roger Daltrey. "We've gone off on slightly different directions; Roger's been working with a new band; I've been developing new music and writing a book about my life ["Who I Am," published this fall].

"We've really struggled to find something to do this time. We've been anxious to work together -- before we drop dead."

The 'other' rock opera

If "Tommy," released in 1969, wasn't the first rock opera -- the dubious honor is often given to a '60s British band called Nirvana -- it was at least the first one billed that way.

The Who toured "Tommy" hard in 1969-70 and Townshend immediately got to work on a second rock opera, "Lifehouse," a sci-fi story of a dystopia saved by music. Much to his dismay, the other members didn't like the concept, so those ideas were funneled into the 1971 album "Who's Next."

In the spring of 1972, Townshend set out to pen a new rock opera in which he would stay inside the head of his hero. A note he scribbled to himself read, "trace the late teens of a kid to the point he experiences a lot of things that [mess] him around," he writes in "Who I Am."

After the strain of writing and touring "Tommy" and "Who's Next," the guitarist, back with his family, was not only exhausted, he writes, "I felt cold, depressed, tragic, lost and hopeless." His mind went back to a night in 1964, when he was 19 and spent a few hours sleeping under a bridge with friend Liz Reid after an incident where rival British gangs the Mods and Rockers rumbled.

He quickly outlined the story of Jimmy Cooper, a teenage Mod with "quadrophenic" sides to his personality, reflecting the members of the Who: a tough guy (Daltrey), a romantic (John Entwistle), a bloody lunatic (Keith Moon) and a beggar, a hypocrite (Townshend).

The Vespa-riding, amphetamine-popping Jimmy takes part in the Brighton youth riots against the leather-clad Rockers, loses his girl to his friends, is brushed off by his favorite band, becomes disenchanted with the Mods, and ends up adrift on a boat where he reaches a point of self-revelation.

"The rule we established during the recording was that energetic musical rage would be used throughout," Townshend writes. "We didn't need throwaway tracks for light relief, we didn't need light and shade, irony or humour."

He notes that "apart from Keith's occasional antics," recording it was a "joyful experience" and that's exhibited in the ambitious performance. Moonie is his usual manic self on drums, Daltrey digs deep and turns in some of his most guttural vocals, while Entwistle not only holds it down on bass but broadens the sound with an array of horns. Not only is Townshend's mix of subtle acoustic and windmilling electric guitar work magnificent throughout, but he added everything from synths to banjo, and also recorded all of the record's ambient sounds, from seagulls to the rain.

The Two

Moon stuck around for two more albums before dying in 1978 of a drug overdose after a long bout with alcoholism. Entwistle died of a cocaine-induced heart attack on the eve of the band's 2002 tour. Since then "The Two" -- plus bassist Pino Palladino and drummer Zak Starkey -- have carried on for four tours, one album (2006's forgettable "Endless Wire"), and a much-derided Super Bowl halftime show in 2010.

Townshend, 67, and Daltrey, 68, chose to pull "Quadrophenia" out of mothballs, in part because the guitarist considers it to be the band at its peak. Also, he noted at the teleconference, "For me it's very easy. When I wrote it, I wrote it pretty much all on guitar -- there are a few keyboard bits -- but so everything falls under my fingers, it flows very naturally."

He acknowledged that for his curly-haired counterpart, it's "a taxing vocal piece," a challenge the singer embraces.

"I don't know how many more years I'm going to be able to sing this music," Daltrey said. "My voice is great at the moment, so I'm just going to explore the possibilities that one time I might sing 'Quadrophenia' and it's a little bit easier."