In the middle of their set at the Paramount a couple weekends ago, surrounded by windmilling guitarists and kit-smashing drummers, one of Modest Mouse's new members pulled out a trumpet. A couple weekends before that, tourmates-to-be Man Man tooted a trumpet at Neumo's. Tapes n' Tapes record with a trumpet. Cake have always included one. The Arcade Fire, Calexico, Weezer, the Apples in Stereo, Belle & Sebastian, British Sea Power—a slew of indie bands keep a trumpet on hand, ready for when the moment calls for that flood of brightness. Not a horn section—just a trumpet.
At some point in the last few years, trumpet became the go-to horn for discerning rockers, replacing its de facto counterpart, the saxophone.
We can all agree that the sax—the instrument that connected pop music with its soul to produce the earliest crossover hits, like Sam Cooke's "Twistin' the Night Away" in '62 and Jr. Walker's "Shotgun" in '65—is now the jeans-and-sport-coat of rock. But, somehow, the trumpet never lost its edge. In fact it's just now finding it, rarely utilized in the classic rock of yore but coming into its own as a standard instrument in the indie-rock arsenal.
Certainly it comes down to sound: Sax sounds like soul, which makes it easy to exploit and obvious when it's misused. Misuse results in cheesiness, and cheesiness leaves an indelible stink.
Trumpet sounds like more than that—it's the sound of soul and smarts, pathos and humor, from mariachi to Modest Mouse. There are technical, tangible reasons why.
The saxophone's reed—a slice of dried cane that vibrates within the mouthpiece to achieve that goosey hum—creates a disconnect between the lips and the metal and offers numerous ways of positioning the tongue and holding the mouth. It's far easier to produce overtones with a sax, micro-harmonies that fool the ear into hearing a sound bigger than what's being blown. Its rich, chocolaty sound can easily overwhelm its accompaniment.
The trumpet's mouthpiece, on the other hand, is constructed for skin-on-metal contact. It's pure brass and so is its tone. It's the difference between playing acoustic and electric guitar—one is a step removed from its source and therefore encourages flightier flights and geekier effects while the other stays necessarily grounded by its limitations.
Along the same lines, the sax is studded with innumerable valves and keys. The trumpet has three. There's a pleasing minimalism to the trumpet's construction that not only looks cleaner but demands its player do more with less. It requires less technical mastery, which means it attracts less wankery and more innovation.
Saxophone was initially the realm of spiritual seekers mired in earthly temptation—Charlie Parker and John Coltrane brought the instrument to popular consciousness by trying to transcend it. To this day, Parker and Coltrane are appreciated almost exclusively by jazz aficionados or fans of "serious" music.
In the '60s, Motown was the single greatest factor in popularizing the sax (and its ubiquity spelled its eventual demise in the hands of whiter wannabes). Charismatic virtuosos like Jr. Walker and King Curtis distilled the saxophone's juke-joint sauciness into the perfect lube for nascent rock 'n' roll. Squalling and forceful, sax almost always took the lead spot over guitar, which tended toward the more textural and syncopated. Rock 'n' roll copped: That driving Motown sax sound is often the same one you hear on Nuggets comps, right up until Bruce Spring-steen made Clarence Clemons his mascot and made a juke joint out the blue-collar bar that was the Stone Pony. From that point on, sax was the horn of the people and would never be the same.
Trumpet, though, has as its sole ambassador Miles Davis, a musician even the most casual music fan understands to be impeccably cool. As an innovator, who else comes close? Dizzy Gillespie? A terrific player and bandleader, but hardly the alpha male Miles was. Wynton Marsalis? A stick-in-the-mud traditionalist. That's pretty much the end of the list. Nobody's even tried to wrest the trumpet's legacy from Miles, which is what leaves it wide-open for borrowing by outside-the-box indie rock bands. Its only legacy in rock is late-era Miles—Bitches Brew, Live Evil, etc.—the hard fusion style that attracted attention from Hendrix and Prince. There is no saxophone equivalent. Nor is there a trumpet-playing counterpart to Kenny G.
Rock is nothing if not mercurial, though, and newcomer Chris Botti is nothing if not a trumpet-toting, bullshit-crooning Kenny G with a better stylist. Thanks to bands like Menomena and the Rapture, who take the saxophone to wildly experimental and soulfully goofball places, sax has recently eked a smidge of credibility in rock. But even as tastes and tones shift, trumpet and saxophone will never stand on equal footing. There isn't enough room on the stage. 
