Liszt spent nearly seven years on an Italiante opera, Sardanapalo, based on Lord Byron's tragedy of 1821. Working intermittently on the project, he abandoned a continuous draft in 1852.
The surviving music constitutes the entirety of Act 1 (minus its final cadence), given in various degrees of full and shorthand notation. The style is a unique mixture of Italianate pastiche and mid-century harmonic innovation.
The manuscript (GSA 60/N4) contains:
Scena ed aria for soprano,
Scena e duetto for soprano and tenor,
a grand Terzetto finale for soprano, tenor and bass-baritone.
I am currently finishing a critical edition of what survives from this work for Editio Musica (Neue Liszt Ausgabe), and an orchestration of Liszt's score--drawing on the instrumental cues he specified in the manuscript--for Schott Music. The results will be published in 2019.
Project updates are available here
Eugène Delacroix, The Death of Sardanapalus
(Musée de Louvre, 1827)
Click for a couple of German radio interviews: