Gloria Coates (October 10, 1938 in Wausau, Wisconsin) is an American composer who has lived in Munich, Germany since 1969. She studied with Alexander Tcherepnin, Otto Luening, and Jack Beeson.
Her music features canonic structures and prominent, sometimes exclusive, glissandos, being "characterized by extremely strict, even rigid technical procedures (canonic structures), which are often worked out with unusual musical materials (glissandi)". Her music is postminimalist, marked by the tension "not only between material and technique (...an attempt to give structure to chaos), but even more so between what would have to be termed 'sober-technical' compositional principles and the genuine direct expressive power and emotionality of the music".
As one interview describes:
For Gloria Coates, artistic expression is a spiritual necessity. She has great interest and significant participation in painting, architecture, theater, poetry, and singing—but it is through composing that she taps into a wellspring of abstracted emotionality that the others cannot reach. Whatever the veiled expressions of her work may be, there is an undoubted emotional richness present, which if not concretely knowable is at least viscerally felt by the audience. Canons constructed of quartertones and glissandos evoke gloomy instability, but also unearthly beauty.
Mark Swed: “Coates is a master of microtones, of taking a listener to aural places you never knew could exist and finding the mystical spaces between tones.” 
As is described by Kyle Gann' liner notes to one of her albums:
Behind the variety of such techniques, behind even the varying deployment of similar structures, one hears Coates's constant aesthetic: her sense of each movement as a unified gesture, her almost post-minimalist unidirectionality. Above all, while sadness, anger and mysticism appear in her work with stylized clarity, they are subsumed to an overarching tranquility that often has the last word, and always the most important one.
In Kyle Gann's article "A Symphonist Stakes Her Claim", Gloria Coates was crowned, "the greatest woman symphonist", for her passionate pursuit and persistence in a domain that is dominated by men. However, this ambitious pursuit to be a woman symphonist has not been a conscious effort to set herself apart from the other female composers, instead in an interview she commented that it came through a natural manifestation trying to convey something deep within her. "When I did, I thought, 'That's really gutsy of me to call it a symphony,'" she said from her home in Munich, "I always had an idea of symphonies being in the 19th century, somehow. I never set out to write a symphony as such. It has to do with the intensity of what I'm trying to say and the fact that it took 48 different instrumental lines to say it, and that the structures I was using had evolved over many years. I couldn't call it a little name."American Composers Forum member bio: Gloria Coates at the Wayback Machine (archived July 16, 2011)  Hunter, Trevor. "Gloria Coates: Beyond the Spheres", NewMusicBox.org. In conversation with Trevor Hunter July 11, 2008–3:00 p.m. at the home of Catherine Luening. Gann, Kyle. Sunday, April 25, 1999. "A Symphonist Stakes Her Claim", The New York Times.
Besides composing, Gloria Coates also paints abstract expressionistic paintings that are often used as the covers for her albums. In her paintings, complementary colours such as red and green, yellow and blue, interact and mix with one another in the small strokes. The painterly manner, with layers of swirls of colours, is reminiscent of the style of Vincent van Gogh.
The following is a chronological list of Coates' musical compositions:
1950The Sighing Wind
1961SylkenTe DeumDies SanctificatusThieves' CarnivalThe Rainy DayTwilight
1962SonatinaTrio for Piano, Flute and OboeGlissando String QuartetEveryman. Morality PlayFive Abstractions
1963Rondo for Flute, Oboe, Bassoon, Tambourine and Field DrumO Sing Unto the Lord a New Song
1964Interlude for OrganMathematical EquationsMissa brevisOverture to Saint JoanSaint JoanString Quartet with Provincial Drum
1962/66Fall of the House of Usher
1966String Quartet No. 1Trio for Three Flutes
1971We Have Ears and Hear Not Point Counterpoint
1972Mobile for String QuartetString Quartet No. 2Eine Stimme ruft elektronische Klänge aufNaturstimme und elektronische Klangbänder for Vocal Multiphonics and Modulator
1972/73Natural Voice and Electronic ModulatorCantata da Requiem WW II Poems for PeaceTones in OvertonesFragment from Leonardo's Notebooks "Anima della Terra" Vita
1973Symphony No. 1 Music on open Strings
1974PlanetsHalley's CometMay the Morning Star Rise
1975Five Abstractions of the Poems by Emily Dickinson for Woodwind Quartet Five Pieces for four WoodwindsFragment from Leonardo's Notebooks "The Elements"Neptune OdysseyString Quartet No. 3Variations on "Lo! How a Rose"Memories of ChildhoodMy Country Tis of TheeTextures and Shades of E.D.The Tune without the Words
1976From a Poetry Album
1976/77String Quartet No. 4
1978Symphony No. 3 Symphony NocturneSix Movements for String QuartetEcology 1Ecology 2BetweenThe Beatitudes
1974/82Sinfonietta della notte
1976/82Fragment from Leonardo's Notebooks "Fonte di Rimini" Sinfonia BrevisSpring Morning in Grobholz' Garden
1982Go the Great WayColony Air
1985Choral Symphony No. 5 Three Mystical SongsMeteor March
1986Music in Microtones
1974/88Symphony No. 2 Illuminatio in Tenebris, also: 'Music in Abstract Lines'The Force for Peace in War
1988Breaking ThroughFiori alto recorder and tapeFiori and the Princess alto recorder and tapeSeven Songs with Poems by Emily DickinsonString Quartet No. 5Fiori flute and tapeFiori and the Princess flute and tapeBreaking Through IILichtsplitter for Flute, Harp and ViolaLichtsplitter for Flute, Harp, Viola and 1 PercussionistTo Be Free of ItDramatic Scene The SwanReaching for the Moon
1974/89Star Tracks Through Darkness
1978/89Five Songs on Poems by Emily Dickinson
1984/90Symphony No. 4 Chiaroscuro
1990/91Symphony No. 7 (Dedicated to those who brought down the Wall in PEACE)
1991Indian SoundsSymphony No. 8 Indian SoundsRainbow Across the Night SkyBlue Steel BentBlue FlowersIn the Glacier for 10 flutists and percussionWir Tönen AlleinCette Blanche Agonie
1992Royal Anthem KönigshymneUngeziefer InsectsIn the Mt. Tremper Zen Monastery
1993Castles in the AirIm Finstern sei des Geistes Licht und SonneOlympic Roller Blading
1988/94Time FrozenSymphony No. 6 Time FrozenBlue MondaySperriges Morgen
1993/94The Quinces' Quandery: Homage to Van GoghSymphony No. 9 The Quinces QuandarySymphony No. 10 Drones of Druids on Celtic Ruins
1996Lyric SuiteHeinrich von Ofterdingen. Hommage a Novalis
1997Fairytale Suite Märchen SuiteFloating Down the Mississippi
1965-9815 Songs on Poems by Emily Dickinson
1998Ode to the Moon
1998/99Symphony No. 11
2000String Quartet No. 6Im Ausland
2000/01Symphony No. 12Symphony No. 13Sonata for Violin Solo
2001String Quartet No. 7
2001/02String Quartet No. 8Sonata for Piano No. 2
2002Prayers without Words
2003Lyric Suite No. 2MirageSymphony No. 14
2004/05Symphony No. 15
2007String Quartet No. 9 Compiled: February–April 2003. This list of compositions is based on the "Werkverzeichnis" compiled by Christa Jost. A further source was Gloria Coates' America Music Center website.
Albums (incomplete)Kreutzer Quartet (2002) - String Quartets Nos. 1, 5, 6 (Naxos 8.559091)Kreutzer Quartet (2003) - String Quartets Nos. 2, 3, 4, 7 and 8 (Naxos 8.559152)Kreutzer Quartet (2010) - String Quartet No. 9, Solo Violon Sonata, Lric Suite for Piano Trio(2006) - Gloria Coates: Symphonies Nos. 1, 7 & 14 (Naxos 8.559289)Symphony No. 15 (2004–2005), Cantata da Requiem (1972), Transitions (1984) (Naxos 8.559371)
Vienna Radio Symphony Orchestra/Boder, Teri Dunn (sop)/Talisker Players, Ars Nova Ensemble Nuremberg/Heider
5. Swed, Mark. Saturday, November 15th, 2014. "Gloria Coates' great oddity on display at REDCAT", Los Angeles Times.