The discovery of Doris Dennison's score represents a genuine musicological breakthrough -- what once would have been "a tree falling in the woods" thirty years ago now holds the potential to render "a thunderous clap in our minds." While researching Anna Halprin's lesser-known collaborators, scholar Tom Welsh uncovered the archives of AA Leath, one of Halprin's principal dancers. Buried within these materials was Dennison's handwritten score for Earth Interval, dated May 1956. Born in Saskatchewan, Canada, in 1908, and raised near Seattle, Dennison (1908-2009) encountered John Cage while teaching Dalcroze eurythmics at the Cornish College of the Arts. She joined Cage's earliest percussion quartet -- alongside Margaret Jansen, the composer and his wife Xenia -- in the group widely regarded as having performed the first complete concert of percussion music in the United States. This historic December 1938 concert was followed by tours and the landmark May 1941 performance at the California Club, comprising Cage and Lou Harrison's Double Music, the premiere of Cage's Third Construction, and Harrison's 13th Simfony. As Bradford Bailey observes in his extensive liner notes, Earth Interval demonstrates "an extraordinary balance of elements that imbues the piece with a sense of clarity, directness, and constraint that is both distinct and ahead of its time." The work's most remarkable innovation lies in its approach to extended techniques, particularly Dennison's notation for the central movement. The temporal sophistication of these manipulations anticipated Karlheinz Stockhausen's Mikrophonie I (1964) and Annea Lockwood's water-based sound investigations by over a decade. Comprising three movements "Land Form," "Air Tide," and "Earth Play," Earth Interval is scored for recorder, drums, gongs, maracas, muted gongs, and bowl gongs. When viewed in historical context, placed in contrast to roughly contemporaneous avant-garde percussion works by Cage, Harrison, Louis Thomas Hardin (Moondog), and Harry Partch, or important precursors like Edgard Varèse's Ionisation (1931) and Henry Cowell's Ostinato Pianissimo (1934), it's clear that Dennison was following her own path. This recording by Chicago's Third Coast Percussion, captured in March 2022, represents the first complete documentation of this pioneering work. The present Blume edition, featuring Third Coast Percussion's authoritative interpretation, includes a lavishly illustrated 16-page booklet designed by Bruno Stucchi/dinamomilano, containing complete scholarly apparatus, historical photographs, and detailed production notes.