PORTLAND, Ore. (TheStreet) -- When last we left Trent Reznor, the Nine Inch Nails frontman was in a Twitter fight with the Grammy Awards over his show-closing performance that the event's broadcast cut short.

Both he and Queens Of The Stone Age singer Josh Homme sounded off about the lack of respect, the indignity of losing an award to Imagine Dragons and their displeasure with the whole affair in general. We suggested that Reznor and Homme sounded like old rockers grumbling their way into irrelevance. For Reznor, the curmudgeonly evolution had just begun.

This week, Reznor and Nine Inch Nails announced a summer tour they're co-headlining with Soundgarden. They made sure to note that the tour would kick off at the Planet Hollywood hotel and casino in Las Vegas and end at the Hollywood Bowl in Los Angeles. It just didn't mention the venues in the middle.

They somehow failed to bring up the DTE Energy Music Center in Clarkson, Mich.; The Susquehanna Bank Center in Camden, N.J.; Farm Bureau Live in Virginia Beach, Va.; The MIDFlorida Credit Union Amphitheatre (formerly the 1-800-ASK-GARY Amphitheatre) in Tampa, Fla.; or The Sleep Train Amphitheatre in Chula Vista, Calif. That's right: The summer "shed show" circuit, where they'll be wedged in between nostalgic double bills like Journey/Steve Miller Band, Kiss/Def Leppard, Peter Frampton/Doobie Brothers and Chicago/REO Speedwagon. In their case, however, they'll just be the '90s "alternative" version of Chicago/REO Speedwagon.

This isn't a criticism of either Nine Inch Nails or Soundgarden. It's just the way music works.

Both Nine Inch Nails and Soundgarden are 20 years removed from their best-selling albums -- 1994's The Downward Spiral (quadruple Platinum) and Superunknown, respectively. While Nine Inch Nails has been releasing new material steadily since that time and has expanded well beyond the boundaries of what it accomplished in the '90s and early 2000s, it maintained its critical acclaim and music geek cred, but lost its broader appeal. Soundgarden, meanwhile, just went on a 16-year hiatus after 1996's Down On The Upside while lead singer Chris Cornell embarked on a solo career and Audioslave -- his modern rock venture with the remains of Rage Against The Machine. Their 2012 return album, King Animal, was well-received but lightly purchased.

As we mentioned in the piece about Reznor and Homme, these bands still have the skill and following to draw well on the road, but just aren't as relevant to music at large as they were in their heyday. Nine Inch Nails drew from techno, industrial and house music in the '90s as bands like KMFDM and Ministry did, but had little use for hip-hop or electronic dance music. Cornell experimented when he could, but ultimately hued his solo and Audioslave sound to something Soundgarden fans would be comfortable with. When Soundgarden reunited, Cornell's return to the old material wasn't as dissonant as, say, Justin Timberlake performing an NSYNC song.

But the shed show circuit isn't about broad relevance, but the personal connection. To fans who go to their summer shows, REO Speedwagon is as relevant today as they were in their prime. Journey fans around the world consider that band, even with singer Ariel Pineda instead of Steve Perry, to be relevant to this day. Those bands are relevant in fans' lives, even if they're making only token contributions to the music world at large.

If anything, Nine Inch Nails and Soundgarden should feel lucky that they've stayed off the nostalgia trail for as long as they have. Twenty years after their last Top 10 album, 1984's Wheels Are Turning, REO Speedwagon was playing shows with Styx and touring off of nearly a dozen hits records and live albums. Journey, meanwhile, has had only one platinum album since 1996's Steve Perry-sung Trial By Fire -- 2008's Revelation and it featured re-recordings of the band's early hits. Though Journey still produces new material and has a massive global following, it proudly digs into that back catalog for its shows here in the U.S.

Besides, the shed-show circuit isn't all terrible. Just ask Nelly. Andrew Winistorfer (@thestorfer) at Vice's Noisey music blog wrote a phenomenal piece last year about seeing the multiplatinum-selling, rapping/acting pride of St. Louis hip-hop last year at the Summerfest music festival in Milwaukee last year. Despite selling 20 million records between 2000 and 2009, Nelly was listed behind Talib Kweli, the Spin Doctors, Blues Traveler, REO Speedwagon, Foreigner, the Airborne Toxic Event, Imagine Dragons, Alice Cooper, Billy Idol, MGMT and Styx, among others, on the event's bill.

So how did Nelly handle it? By busting out a mashup of a greatest-hits set -- Air Force Ones, Ride Wit Me, E.I., Country Grammar, Dilemma and Shake Your Tailfeather included -- and basically tearing the roof off of the place. By getting the audience to have fun and by making money doing so. That's it.

Right now, there's no disputing Nelly's influence on hook-singing rappers like Drake, Kid Cudi, Big Sean and others, but there's going to be a time when that legacy fades into the same echo as Soundgarden's or Nine Inch Nails'. The former has sold 20 million albums wold wide and seen its influence spread, at best, in groups like Dillinger Escape Plan and Queens Of The Stone Age and, at worst, the fetid waste of '90s and early 2000s rock radio that called itself "post-grunge."

Nine Inch Nails, meanwhile, is revered by no less than David Bowie and Peter Gabriel and echoed by similarly synthy, cynical, aging progeny including The Knife, EL-P and Crystal Castles. The NIN sound became the soundtrack to Dystopia, with Reznor's work cropping up in Call Of Duty video game sequels and winning an Oscar for its role in The Social Network. With each passing year, that influence grows more faint and tangential as both Nine Inch Nails and Soundgarden move deeper into popular music's ancestry. While Nelly has the luxury of being an elder statesman in one of popular music's most prominent genres, both Soundgarden and Nine Inch Nails have seen their corners of the rock world retreat into shrinking niches.

Those niches still come out to shows -- Billboard notes that concert attendance was up 27% last year after years of post-recession decline -- but they're not filling football stadiums or arenas anymore. They're older, more nuanced and have come to value a seat under an awning or a blanket on the grass more than a spot at the edge of the pit. They don't appreciate what they're hearing any less, but they're just not listening to all that much anymore.

They've come to inhabit the same compartmentalized corner of the music world as their bands have. That little space turns out to be roughly the size of an outdoor amphitheater and its shed.

-- Written by Jason Notte in Portland, Ore.

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Jason Notte is a reporter for TheStreet. His writing has appeared in The New York Times, The Huffington Post, Esquire.com, Time Out New York, the Boston Herald, the Boston Phoenix, the Metro newspaper and the Colorado Springs Independent. He previously served as the political and global affairs editor for Metro U.S., layout editor for Boston Now, assistant news editor for the Herald News of West Paterson, N.J., editor of Go Out! Magazine in Hoboken, N.J., and copy editor and lifestyle editor at the Jersey Journal in Jersey City, N.J.