I've heard Stevie Wonder's "Superstition" hundreds of times before, but this time it's a revelation. Instead of the churning pool of funky clavinet licks and flaring horns, I'm just hearing Wonder's voice solo. It's garlanded with a slight audio bleed, as if there's a tinny transistor radio nearby, piping out all the other instruments. I click the Solo button and choose the next instrument I want to hear: first, skeletal horn parts; then, a bloopy bass lick; and finally, amazing, polyphonic layers of echoing clavinet lines.

"I can't believe we're hearing this," exclaims a veteran recording engineer I'm visiting in New York. We're analyzing some of the multitrack recordings that have recently surfaced online. I noticed them on a discussion board, where a subject line jolted me out of my seat: "Have you heard any of the 'multitrack masters' that are floating around on the internets?" The accompanying list—which includes Marvin Gaye's "What's Going On?" "She's Leaving Home" by the Beatles, and Queen's "Bohemian Rhapsody" as well as songs by Nirvana, Bob Marley, Def Leppard, and Jimmy Eat World—was tantalizing and seemingly random. I was amazed that such secret, closely guarded treasures might be available to anyone with a decent computer and a fast internet connection. Here's why.

Most music recorded since the late 1950s has employed multitrack recording; each instrument or group of instruments, such as the lead vocal, guitar, or string section, gets stored discretely on old-school magnetic media (along actual "tracks" on tape) or written to a spinning hard disk like the one that stores data in your computer.

Think of it as a musical MRI scan or a giant, multistave orchestral score for pop music. Whether musicians play together "live" in a room or come in at different times to add (i.e., "overdub") their parts, multitrack recording enables the artist, producer, or anyone to examine, add, subtract, and transform what happened in the recording studio.

Before we cued up "Superstition" in Adobe Audition, the engineer, active in the industry since the 1970s, surmised that the audio might have been leaked by a bored studio intern or a DJ commissioned for a remix. Others have theorized that the tracks escaped from the exclusive orbit of vendors who demo the industry standard (and appallingly restrictive) multitracking software Pro Tools.

I hope more "multitrack masters" surface; they not only exhume the latent avant complexity of classic pop hits but also offer an incomparable way for anyone to learn, explore, and experiment with music. recommended

Hunt for the various multitrack masters online by Googling "MultiTrack" and the aforementioned artists. To hear the files, use Adobe Audition or Audacity, a freeware application available at audacity .sourceforge.net.

Classical and Avant-Garde Calendar

Thurs 8/28

THE FORTY PART MOTET

Successful sound installations foster (or at least insinuate) new and unexpected relationships between sounds, spaces, objects, and people. Mediocre sound installations—or worse, a bunch of stuff in a room with a soundtrack—often camouflage a concert and provide a venue for composers with no other prominent avenues to reach the public. Janet Cardiff's The Forty Part Motet erases the boundaries of the concert hall by surrounding the listener with 40 speakers; each speaker "sings" a part in Thomas Tallis's 1573 40-voice motet Spem in Alium. Cardiff's genius is to allow you to do what cannot happen in traditional live performance—get close, wander among the voices, and decide whether to listen as a performer, spectator, or something in between. Not to be missed. Closes Sun Sept 7. See www.tacomaartmuseum.org for the final weekend's extended hours. Tacoma Art Museum, 1701 Pacific Ave, Tacoma, 253-272-4258, 10 am–5 pm, $7.50.

LAYLA ANGULO

After a bit of woodshedding, the singer and saxophonist returns with a new album, Mientras, studded with top-notch guests including Arturo O'Farrill and former Irakere flutist Orlando Valle. Here, Angulo celebrates the release of Mientras with a first-rate band with Paquito D'Rivera's bassist Oscar Stagnaro. The Triple Door, 216 Union St, 838-4333, 7:30 pm, $15.

JAZZ: THE SECOND CENTURY

The final installment of this Earshot Jazz project features a double bill, Pontius Pilots and drummer Byron Vannoy's Meridian. I like how the Pilots—the duo of keyboardist Victor Noriega and sampler-meister Robert Nelson—unapologetically blend acoustic piano and electronics without smothering the music. They leaven transitions between songs with careful pauses and well-timed silence; rhythm tracks appear then evaporate while Noriega deftly inserts riffs, lone notes, and sinewy melodies. By contrast, Vannoy's Meridian ensemble strives to continue the exploration charted on Miles Davis's still-fertile Filles de Kilimanjaro with a few cheery, boppish tunes added in. Fourth floor Chapel Performance Space, Good Shepherd Center, 4649 Sunnyside Ave N, 547-6763, 7:30 pm, $10.

Fri 8/29

MONKSTONE THEOCRACY

Ah, the sweetly discordant and secretly sentimental compositions of legendary jazz icon Thelonious Monk. "The music keeps you on track," vouched Monkstone Theocracy pianist Bill Anschell when I interviewed him last summer. "You won't play a string of eight notes or swing-inspired melodies. Monk's music has a spirit of its own. Monk brings humor into jazz without making fun of what he's playing or being cheesy." Amen. With Christopher Woitach on guitar. Hiroshi's Restaurant, 2501 Eastlake Ave E, 726-4966, 7:30–10 pm, free.

GUST BURNS LARGE ENSEMBLE

The composer and pianist convenes fellow improvisers to range through works that embrace surprising timbres and contrasts between collective action and individual expression. Fourth floor Chapel Performance Space, Good Shepherd Center, 4649 Sunnyside Ave N, 789-1939, 8 pm, $5–$15 sliding scale donation.

Sun 8/31

COMPLINE CHOIR

Circa AD 530, St. Benedict outlined seven offices to be spoken and sung. Compline, the last holy office of the day, is sung after dinner, hence the late Sunday start time. The cathedral is refreshingly cool this time of year, so bring something to don over that too-tight T-shirt. St. Mark's Cathedral, 1245 10th Ave E, 323-0300, 9:30–10 pm, free.

Tues 9/2

FIRST TUESDAYS

The Early Music Guild inaugurates an ongoing series devoted to chamber performances of Baroque and pre-Baroque music. Grand Cru, a whimsical moniker for the duo of harpsichordist Bernard Gordillo and flutist Kim Pineda, perform pieces by J. S. Bach, Jean-Marie Leclair, Joseph Hector Fiocco, Michel Blavet, and the ubiquitous Telemann. Trinity Parish Church, 609 Eighth Ave, 325-7066, 7:30 pm, $10/$20/$25.