Critics hailed it as a defining moment in mid-20th-century music, with The New York Times describing it as the "first sonata truly to come of age by an American composer of this period".

However, progress was slow due to his demanding schedule, which included preparations for his ballet Medea and Knoxville: Summer of 1915.

A planned retreat to the American Academy in Rome to focus on the sonata proved unproductive, as Barber was distracted by the postwar social scene and his interactions with intellectuals, Vatican insiders, and Italian culture.

Initially, Barber envisioned a three-movement work, but after sharing his progress with Horowitz, the pianist suggested a four-movement structure with a "flashy last movement".

He followed this premiere with a private performance in New York in early January 1950 attended by prominent composers including Aaron Copland and Gian Carlo Menotti.

[3] However, Barber's progress on the sonata was interrupted by a hectic schedule that demanded his focus, including rehearsals for his ballet Medea and plans for Knoxville: Summer of 1915.

However, once in Rome, he found it hard to focus, with the change of scenery and the charm of Italy's culture and people distracting.

Barber was distracted by the postwar social and political scene, engaging with intellectuals, Vatican insiders, and historical interests like an excavation near Cosa.

Despite attending inspiring concerts, including programs of newly discovered Vivaldi pieces, Barber struggled to accomplish much during his stay.

[4] Barber returned to the United States early in the summer, sooner than planned, and finished the second movement in mid-August of 1948.

[7] The composer finished the sonata in June 1949, and Vladimir Horowitz began to prepare it for performance, spending five hours a day practicing it.

Gian Carlo Menotti, Virgil Thomson, Douglas Moore, William Schuman, Thomas Schippers, Aaron Copland, Lukas Foss, Myra Hess, and Samuel Chotzinoff all attended.

[20] Tischler also notes that the sonata follows Beethoven's example in terms of motivic development, seriousness, and concentration.

[21] Despite forays into twelve-tone technique, and its chromaticism and dissonance, the sonata is based on a key center, that of E-flat minor.

[18] Musicologist Barbara Heyman writes that in this movement "the sonata form is more aptly delineated by melodic design than by harmonic structure".

The composer prioritizes the musical motive over strict adherence to a twelve-note structure, allowing flexibility in note repetition, omission, and grouping to enhance the piece's expressive quality.

The section begins with a bass ostinato featuring a reworked quintuplet motive, creating a striking effect.

Tischler notes that "the employment of the twelve-note rows in this movement is quite original and a real contribution to contemporary technique", and is a reinterpretation of the traditional passacaglia through a 20th-century lens.

[23][47] While conventional in structure, syncopated rhythms and "blue note" harmonies, characteristic of American jazz, are woven into the fugue's fabric.

[53] Throughout the episode, there are allusions to American Western folk music and Barber's earlier piano composition Excursions,[54] and it provides a lyrical contrast to the intense momentum driving the rest of the movement.

[55] The coda begins with a sinister gallop[56] leading way to a passage where the right hand arpeggiates a German augmented sixth chord in E-flat minor, but with an added dominant (B-flat).

[58] Heyman stated that perhaps no other piece by Barber "has had as stunning an impact on the American musical world as his Sonata for Piano".

Richard Keith wrote in The Washington Post following Horowitz's January 11, 1950, Constitution Hall performance that the fugue is "one of the most musically exciting and technically brilliant pieces of writing yet turned out by an American";[60] Glenn Gunn of the Washington Times-Herald said "the sound of the instrument has not been exploited in a similar manner by any twentieth-century composer".

[67] The world premiere recording of the sonata was made by Vladimir Horowitz in May 1950 at New York's Town Hall for RCA Victor.