In a passage not included in the first edition of her collection of memories of Mahler, Natalie Bauer-Lechner records Mahler as referring to this work as dating from after the composition of Die Türken and before his acceptance at the Vienna Conservatoire (NBL2, 69):

Später komponierte ich dann schon fleißiger aus eigenem Antrieb: eine Klavier-Violin-Sonate, eine Nocturne für Cello; für das Klavier alles mögliche, und endlich eine Oper, zu der eine Schulkollege den Text mit mir schrieb. Auf Grund dieses Bruchstückes (denn ich kam nie dazu, sie zu vollebden) wurde ich später am Wiener Konservatorium von Hellmesberger (diesem Schaf) mit Überspringen von Harmonielehre und Kontrapunkt zu meinem größten Schaden in die Kompositions-Klasse aufgenommen.

Later I certainly composed more diligently on my own initiative: a piano-violin sonata, a nocturne for cello; everything possible for the piano, and finally an opera for which a school colleague wrote the text with me. Later, on account of this fragment (for I was never able to finish it), at the Vienna Conservatoire, to my great disadvantage, I was allowed by Hellmesberger (that dolt) to join the composition class having skipped harmony and counterpoint.

(Mahler's concluding assertion about skipping courses are only partially correct: he attended Robert Fuchs' harmony class in 1875–6 and gained first grade in the annual examination. However, it is true that he was allowed to begin Krenn's composition course despite not having attended and completed as prescribed the first year of the counterpoint class: he did attend the second year of the counterpoint course in 1876–77, but seems to have been dilatory and emerged only with a third grade (see PBGME, p. 73ff.).)

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NBL2, 69; HLG1a 39, 112