Today, Longo is mainly remembered for compiling an almost comprehensive catalogue of the
keyboard works of
Domenico Scarlatti. For many years,
Scarlatti's keyboard sonatas were conventionally identified by their Longo numbers, but these were later superseded by those found in
Ralph Kirkpatrick's catalogue. Longo's Catalogue originated in his landmark full publication of the works of Scarlatti in 11 volumes and implied particular groupings of the sonatas, the chronology of which was later completely revised and differently grouped in Kirkpatrick's 1953 study of the composer. Longo also edited works by
Domenico Gallo. His compositions include, among others, two works for piano four-hands, a serenade and a suite; suites for piano with bassoon with oboe, with flute ==Family life==