“If only I could have done it,” Charles Ives once said. “It’s all there—the mountains and the fields.” The composer was speaking of his dream project, the “Universe Symphony,” which was to have depicted nothing less than the formation, the evolution, and the future of the world, from the rocks below to the heavens above. Ives’s sketches are fragmentary, but they suggest an immensely complex structure in which rhythms, tempos, harmonies, timbres, and tuning systems are superimposed in a cosmic blur. (Two realizations, by Larry Austin and by Johnny Reinhard, give an enticing idea of what might have been.) Ives imagined presenting the work outdoors, with multiple orchestras and choruses positioned on mountaintops and in valleys. The ideal performance might consist of a population playing and singing for itself. Ives never liked concert halls, and in the “Universe” he releases music back into the wild.

I thought of Ives several times on June 21st, when New York joined more than three hundred cities—including Montevideo, Djibouti, Kabul, Hanoi, and Sydney—in celebrating Make Music, a global sonic bacchanal that takes place each year on the summer solstice. The ritual began in France, in 1982, when Maurice Fleuret, a critic turned bureaucrat, proposed that Paris hold a Fête de la Musique, favoring amateur musicians over professionals. The Fête has become an institution, with pop acts filling the Champs-Élysées and classical outfits joining in. (This year’s edition culminated with Pierre Boulez conducting Stravinsky beneath the pyramid at the Louvre.) The New York version, which started two years ago, is somewhat scrappier, although the sum of activity was impressive—more than eight hundred events across five boroughs. There is something subversive, almost Situationist, in seeing two punk girls shouting abrasive lyrics in front of a Village storefront, or in finding a clutch of French-horn players tooting Wagner in Central Park. Such musical disruptions invite urban dwellers to abandon their tight routines and let the rhythms of the city take over.

I began the day at 10:30 A.M., in front of Ollie’s, a Chinese restaurant near Lincoln Center. Teen-aged students from the Kaufman Center, on West Sixty-seventh Street, were performing Terry Riley’s pulse-driven masterpiece “In C,” with a small audience gathered on the sidewalk outside. An electric guitarist supplied a funky tinge, and a violinist added authentically minimalist vocalise. Then I went to Union Square, where a group calling itself the New York Megaphonica chanted self-referential slogans through megaphones. (“People come together to make noise, to make noise.”) By 1 P.M., I was at the East Meadow, in Central Park, for a rendition of Aaron Siegel’s new piece “Science Is Only a Sometimes Friend,” for an orchestra of glockenspiels. A core ensemble played the score, and toy glockenspiels were distributed to the crowd, which had its own instructions: Siegel’s associates held up cue cards to indicate when we should move from one note to another. Several small children chose to depart from the score and improvise freely, their cadenzas giving a jazzy flavor to the hazy, hypnotic clouds of chiming tones.

After checking out John Morton’s “Central Park Sound Tunnel”—a rumbling electronic installation in a passageway near the zoo—and ambling west, I took the No. 1 train to Straus Park, at 106th Street, to see the first few numbers of a hard-driving set by the percussion duo Loop 2.4.3. Then downtown again, to the West Village, where the Yamaha company had parked four pianos in the middle of Cornelia Street, and members of Composers Collaborative, led by Jed Distler, were performing “Canto Ostinato,” by the Dutch minimalist Simeon ten Holt. A light rain had begun to fall; the pianos were protected by tents. I took a sidewalk table at the Cornelia Street Café, ordered a burger, and had the pleasant feeling of entering into a whimsical art movie: the decorous, wistful repetitions of ten Holt’s music lent an air of mystery to the dripping of water from the awning, the gliding whoosh of bicyclists in orange rain gear, and the waitress’s commentary on the menu. It was in the spirit of the day to be charmed rather than annoyed by the accidental music of the city: the beeping of a bus’s wheelchair lift during “In C”; the syncopated barking of a dog energized by the drumming of Loop 2.4.3.

Various Make Music events—the pianos, the glockenspiels, the megaphones, and a gathering of bagpipes on Staten Island, which, regrettably, I missed—articulated a running theme called Mass Appeal: convocations of many instruments of the same type. We were building to the grand finale, New York’s answer to Boulez beneath the pyramid: a presentation of Henry Brant’s “Orbits,” for eighty trombones, organ, and soprano, in the great spiralling rotunda of the Guggenheim Museum. Brant, who died last year, at the age of ninety-four, was one of those cussedly brilliant outsider composers who are never recognized as widely as they should be and seem to prefer it that way. He specialized in summoning flocks of instruments and dispatching them into the cityscape: in Amsterdam, in 1984, he filled four barges with flute players and had them converse musically with church carillons. He was also an orchestrator of genius who made a compelling symphony out of Ives’s “Concord Sonata.” He talked of completing the “Universe,” but never did.

Some of Brant’s works meander, but “Orbits” is a tautly structured score that strikes deeper than its gimmicky-seeming concept suggests. The language owes much to Ives in his ultra-dissonant, prophet-on-the-mountaintop mode, with debts also to the otherworldly cluster harmonies of Henry Cowell, Iannis Xenakis, and György Ligeti. In one thrilling passage, the trombone choir fans out from the note G to make a pulsating mass of eighty separate quarter-tones. The noise at the Guggenheim was extreme—an application on my iPhone recorded a maximum of a hundred decibels—but never gaudy; the piece has episodes of muted, Rothko-like beauty and ends with a ghostly, ancient-sounding chant. The trombonists stood in rows along the spiral; the composer Neely Bruce conducted expertly from the lower part of the ramp, and the audience gathered on the floor below. The golden sheen of the instruments contrasted with the creamy white of the walls and the blue of the skylight above. There were two performances, and I stayed for both, guessing that I would never hear, see, or feel anything like it again.

Two Sundays before Make Music New York, the Brooklyn-based venue Issue Project Room, an indispensable site of offbeat programming, organized its own sonic jamboree. Twenty-one musicians led groups on “soundwalks” around Brooklyn and other boroughs, treating the city either as an audio source or as a stage for their work. (The term “soundwalk” was popularized by the Canadian composer R. Murray Schafer, who, in the spirit of Ives and John Cage, has long blurred distinctions between composed music and ambient sounds.) Two dozen people signed up for a soundwalk with Betsey Biggs, a young Princeton-trained composer and interdisciplinary artist who often creates site-specific performances. Beforehand, Biggs directed participants to a Web site where they could download “Detox Project,” an electronic piece that she had assembled for the occasion. It consisted largely of sounds recorded in and around the murky old Gowanus Canal, in Brooklyn: machine noises, trucks backing up, the bell of a rising drawbridge, sirens, pedestrian chatter, and, for a long while, a voice softly humming a childlike, three-note melody.