As an artist with a compulsion to create, Raff continually was having ideas about potential compositions and, quite naturally, some of these never came to fruition. No doubt most of these passing fancies died without Raff making any record of them. Those projects which are recorded in his daughter's biography of him and in the surviving Raff papers, however, give a tantalising indication of the scope of these musical might-have-beens.
The earliest project for which evidence remains is a song cycle "Todte Liebe" (Fatal love) of around 1855, for which Raff selected 11 poems and actually set three of them. Two of these were subsequently included in his Sanges-Frühling cycle. It is not known why he abandoned composition of this smaller set of songs, having got so far towards completion.
One of Raff's a capella church music works - the Kyrie and Gloria WoO.31 - was probably intended to be part of a Mass which Raff definitely intended to write for the church at which he had been christened in his home town of Lachen. The complete Mass remained unwritten.
A major work which Raff did finish after many years is his opera Samson. The death of the great Wagnerian heldentenor Ludwig Schnorr von Carolsfeld in 1865 robbed the Dresden premiere of its Samson and the work was withdrawn. In the months before his death Schnorr and Raff had seen much of each other and at one of their meetings the singer gave Raff a synopsis for an opera "Dame Kobold" and a libretto which he had written for "Agnete" based upon a Danish Fairy tale.
Schnorr's synopsis eventually bore fruit as Raff's fourth (and only really successful) theatrical work. Although the composer also took the "Agnete" text away with him and it remained in his papers, he never got around to composing the piece.
In the late 1860s Raff considered writing a textbook promoting his views on harmony and composition because, as he told his friend the composer Peter Cornelius, he disagreed with current practice. It never progressed. After his death, however, both his widow and his pupil Edward Macdowell were sure enough of its existance, at least in draft, for the American to offer to edit it and arrange for its publication if Doris Raff could locate it. Only a few random jottings were found.
Raff became principal of the Hoch Conservatory in 1877 and he was able to devote much less time to composition. This didn't prevent his fertile mind from coming up with suitable subjects for future projects, however.
He seems by then to have given up hope of seeing any of his stage works performed but he was not deterred from considering new scenarios. Amongst these are two operas on Spanish themes: a "Don Quixote" and a "Sancho Barbado". Raff also considered a biblical opera, an opera with a local, Frankfurt, setting and an historical music drama "Die Vandalen" (The Vandals). Of each of these ideas his daughter Helene records that nothing remained but "the title and a couple of notes on scrap paper".
A fifth operatic project of the Frankfurt years was a piece centred on the romantic Wartburg - a grand castle near Eisenach in central Germany associated with several medieval legends. Appropriately, the opera was to have been set in the time of the Hohenstaufens - the 12th. and 13th. centuries. It echoed a previous Wartburg project of Raff's from the early 1870s. In a letter to his publishers he refers to a Symphony "Auf der Wartburg". Why he put aside this fascinating idea, full of symphonic possibilities for the composer of "Im Walde" and Lenore is unkown but the inspiration eventually found voice in his "Aus Thüringen" Suite for orchestra, which contains two movements associated with the castle and its legends.
Raff's last great completed work was his oratorio "World's End - Judgement - New World". Two other putative pieces in this genre feature during his Frankfurt years. About the first, "Das Wasser" (The Water), no more is recorded. A second biblical oratorio "John the Baptist" appears actually to have been begun by Raff just before his death - he marked out the intended text in red pen in the bible which he kept on his desk.
Raff's passing also left a couple of other works unfinished. The manuscript of his Duo for Violin & Piano WoO.55 suggests that it may have been intended as the fourth movement of a sixth Violin Sonata. Finally, there is a fragment of an Grand Fugue for orchestra (WoO.56) amongst his papers.