Press play on any gray audio player to hear samples of microtonal compositions.

Imagine drawing a sweeping landscape — Chicago’s lovely skyline, say, or maybe a sunset — but you’re stuck using crayons. If pressed, which would you sooner reach for: a 12-pack of colors or a 64-pack?

In visual art, the answer is obvious: Color is a spectrum, so why not capture more of it? Musical pitch is a spectrum, too — and yet, the notion of using more pitches than the 12 that can be plunked out on a piano remains far outside the mainstream in most Western musical genres. Accustomed as we are today to one type of tuning, those pitches between the keys, called microtones, sound spooky, sickly or just plain “out of tune.”

But microtonal music is having a moment in Chicago, courtesy of a recent record release from local label Cedille Records and the Frequency Festival. This annual celebration of the sonic fringe takes over Constellation in West Lake View from Feb. 20 to 25.

As niche as it may sound, the release of Cedille’s Acoustic Microtonal is due to two collaborators with second-degree claims to mega-fame: Matthew Sheeran, a British composer who is the brother of pop star Ed Sheeran, and Cedille Records owner Jim Ginsburg, who is the son of late Supreme Court Justice Ruth Bader Ginsburg.

Both share a passion for music by the late Chicago-based keyboardist and composer Easley Blackwood, Jr., who taught at the University of Chicago from 1958 to 1997 and passed away last January at 89. As a composer, Blackwood cycled through many styles and phases over his long career. In the 1970s, he became fixated on microtonality. Though other classical composers had used microtonal pitches for decades, Blackwood put a twist on the approach: He wanted to harmonize these unconventional pitches so intuitively they sounded, well, conventional.

“He was trying to find links with the 12-note system rather than blowing it up,” Sheeran said.

Blackwood received a grant from the National Endowment for the Arts to pursue experiments in equal temperament microtonal tunings — in other words, music that splits the octave into more than 12 equal steps. In 1980, he released his Twelve Microtonal Etudes for Electronic Music Media, each of which divide the octave into anywhere between 13 to 24 notes. In composing the etudes for electronic keyboard, he references J.S. Bach’s Well-Tempered Clavier (1722), a formative collection of keyboard etudes that also probed tuning conventions of the time.

Blackwood’s experiments “completely changed” his approach to composition, said Ginsburg, who knew the composer for years. Cedille Records recorded Blackwood’s work at a time when it was overlooked in other musical circles.

“Up till then, pretty much everything he wrote was atonal — and often pretty radically so. But he rediscovered the beauty of tonal writing by writing in these other tunings,” Ginsburg said.

For Acoustic Microtonal, Sheeran arranged Blackwood’s Etudes, originally for electronic keyboard, for a classical chamber ensemble.

Much like Blackwood’s synthesized originals, Sheeran’s arrangements of the Etudes manage to sound familiar to the lay-listener — even beautiful. The fourth etude nods to Indonesian traditional music — Sheeran casts a hyperactive harp to step in for the bell-like percussion choir found in gamelan ensembles. He gives Blackwood’s impressionistic second etude a lush orchestration; far from grating, it sounds like it could have come from the pen of French composer Maurice Ravel, a mainstay on Chicago Symphony programs.

But making the Etudes work on acoustic instruments is a taller order than it seems. Most keyed instruments are designed to be played in conventional tuning. A microtonal pieceBlackwood wrote for guitar, for example, requires refretting the instrument.

To record the etudes for live instruments, Sheeran rewrote and recorded them in conventional tunings that honor the chordal motion and resonances Blackwood evoked. Then, he autotuned the recording sessions — or, more accurately, auto-detuned them. Compare the recording session to how it sounded on the album.

“This was sort of a shortcut, because we didn’t know what it was gonna sound like,” Sheeran said with a wry smile. “Hopefully, this will be a stepping stone for genuinely acoustic performances of these pieces in the future now that we know how nice it sounds.”

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That spirit of experimentation — trying things out for trying’s sake — has been the driving ethos of Frequency Festival since it started in 2016. The festival attracts a mix of local and international acts, including many who rarely perform in Chicago, much less the United States.

Curator Peter Margasak, formerly a music writer for the Chicago Reader, estimates 70% of this year’s bookings engage microtonality or alternate tunings in some way. On Feb. 20, violin/viola duo andPlay performs two works in just intonation, a tuning system based on ratio relationships between pitches. A double bill on Feb. 22 explores harmony from various historical and cultural perspectives, like Hindustani dhrupad, Persian ghazal, Javanese music and now-outmoded European classical tuning styles. The following night, organist Ellen Arkbro retunes the organ at the University of Chicago’s Bond Chapel to conjure ensconcing, unearthly harmonies.

Originally from Buffalo Grove, Ill., and now based in New York, pianist Cory Smythe closes out the festival. In recent years, Smythe, 46, has been burrowing deeper and deeper into microtonality with the aid of a specially tuned MIDI keyboard — a latter-day version of Blackwood’s own microtonal keyboard. Unlike Blackwood, he plays it and a traditionally tuned concert grand at the same time, combining their pitch palettes.