Metamorphosen, study for 23 solo strings (TrV 290, AV 142) is a composition by Richard Strauss for ten violins, five violas, five cellos, and three double basses, typically lasting 25 to 30 minutes.

The piece was commissioned by Paul Sacher, the founder and director of the Basler Kammerorchester and Collegium Musicum Zürich, to whom Strauss dedicated it.

As with his other late works, Strauss builds the music from a series of small melodic ideas "which are the point of departure for the development of the entire composition.

"[3] In this unfolding of ideas "Strauss applies here all of the rhetorical means developed over the centuries to express pain.

But it has other progenitors: the Finale of Mozart's Jupiter Symphony (a personal favorite of Strauss as a conductor) and the Fugue from Bach's Solo Violin Sonata in G minor BWV 1001.

Strauss also used it in the Oboe Concerto, written only a few months after Metamorphosen, displaying "a remarkable example of the thematic links between the last instrumental works".

At the end of Metamorphosen, Strauss quotes the first four bars of the Eroica's "Marcia funebre" with the annotation "IN MEMORIAM!"

In late 1944 and 1945 Strauss sketched some music in waltz time described in his sketchbook as Trauer um München ("Mourning for Munich").

[7] Timothy L. Jackson believes that scholars who interpret the early sketches of München as the origin of Metamorphosen have a weak, even untenable case.

[10] A few days after finishing Metamorphosen, Strauss wrote in his diary: The most terrible period of human history is at an end, the twelve year reign of bestiality, ignorance and anti-culture under the greatest criminals, during which Germany's 2,000 years of cultural evolution met its doom.

Jackson concludes that Metamorphosen is a philosophical, Goethean study of the underlying cause of war in general, humankind's bestial nature.

[8] Michael Kennedy also develops the view that Strauss's chronological rereading of Goethe during 1944 was a crucial influence.

He quotes Strauss as telling a visitor: "I am reading him as he developed and as he finally became...Now that I am old myself I will be young again with Goethe and then again old with him—with his eyes.

Gehabe du dich mit Verstand, Wie dir eben der Tag zur Hand; Denk immer: ist's gegangen bis jetzt, So wird es wohl auch gehen zuletzt.

According to Norman Del Mar, "These lines of searching introspection Strauss wrote out in full amongst the pages of sketches for Metamorphosen, the word metamorphosen being itself a term Goethe used in old age to apply to his own mental development over a great period of time in pursuit of ever more exalted thinking.