From the very beginning of his career, Raff was an inveterate arranger of both his music and that of others. These compositions fall fall clearly into three categories. First, there are piano arrangements of the already popular works of other composers. Then there are the arrangements which Raff made of his own pieces to foster their popularity. Finally, there are the transcriptions of baroque works written with the altruistic motive of improving appreciation of the music of previous musical eras.
In the mid-19th. century potpourris, fantasias and other arrangements of popular melodies, mainly from contemporary operas, were common currency. Piano virtuosi such as Thalberg and Herz (and originally Raff's mentor Liszt too) based their dazzling pyrotechnic displays on the melodies of others. Those who were able to actually see a full opera performance or hear one of the great titans of the piano were comparatively few and so, for performance in the salon or home, more modest pieces gave music from popular opera wide dissemination. There were no accusations of plagiarism or concerns about copyright, either - everyone from Czerny and Liszt down to anonymous publishing house hacks were busy keeping the huge demand satisfied. Composers like Wagner positively encouraged the writing of good quality transcriptions of their works.
Raff composed many such pieces for the piano, stretching from the Fantasie on Verdi's "Maria de Rudenz" op.4 of 1842 to the piano arrangement of Gounod's Valse de Juliet WoO.38 of 30 years later. Most of the operas from which Raff took his material remain familiar to us today - although Kücken's "Der Prätendent", Saloman's "Diamantkreutz" and Raff's own "King Alfred" have not stood the test of time. In all there were a total of 36 works varying from straightforward fantasies intended for playing in the parlour to pieces like the four monumental transcriptions of 1867 forming the Reminiscences of "Die Meistersingers" WoO.26, requiring a virtuoso of a high order to carry them off.
These works were Raff's "Brotarbeit", the work which kept bread on his table, and he found a ready market for them. He'd perfected the arranger's craft whilst working for the publisher Schuberth in Hamburg (for whom he produced a piano arrangement of Beethoven's two Violin Romances WoO.11 in 1849) but his easy hand distressed his friends who felt that he was compromising his artistic standards by churning out what they regarded as pot-boilers. Raff didn't quite see it that way, though it is clear that once he felt secure enough financially, he stopped writing even the more serious transcriptions of contemporary works.
Most composers of Raff's day made piano reductions of their own works. By far the most popular medium was for piano four hands and Raff was assiduous in making such arrangements once he began writing larger scale pieces. Most of his symphonies and orchestral suites were published in his piano duet reductions as were many of his other orchestral compositions, together with a few of his early chamber music pieces and the late string quartets. His concertos and koncertstücks were all available in versions with piano and he also penned piano accompaniments for some of his operas and large scale vocal works. The work was simply good financial sense and helped popularise the music.
Raff also adapted a few of his piano or chamber works because they would clearly also be effective pieces for orchestra. Movements from the piano works Frühlingsboten op.55, Piano Suite No.6 op.163 and "From the Dance Salon" op.174 were all reworked for orchestra. A movement from the Violin and Piano cycle "Volker" op.203 was arranged for violin and orchestra. Raff's two-piano Fantasy op.207 was rewritten by him in an Piano Quintet version.
Many more arrangements were made by other composers of some of Raff's own pieces - particularly of the staggeringly popular Cavatine from op.85, which was arranged for all manner of instrumental combinations, some of which can still be heard today in recordings.
The most altruistic area of activity for Raff as an arranger was his pioneering work in popularising the music of J.S. Bach and other earlier composers. In Raff's day, music was essentially a contemporary art form and audiences had little knowledge of, let alone reverence for, the music of earlier generations. Mendelssohn had pioneered a more historical approach but Raff was one of the first composers to attempt to give modern concert audiences a chance to hear and understand baroque music - by clothing it in pianistic or orchestral colours which would make it more readily accessible to them. In the ten years from 1865 he made piano transcriptions of J.S. Bach's Violin Sonata (WoO.23), the six solo Cello Suites (WoO.30), three Orchestral Suites (WoO.40) and the Chaconne from the Partita for solo violin (WoO.39). He also orchestrated the Chaconne and the "English" Suite (WoO.41). As early as 1859 Raff had transcribed two of Handel's oratorio marches for piano (WoO.22) and his last baroque transcription was the addition of piano accompaniment to four of Benedetto Marcello's Cello Sonatas in 1875 (WoO.42.
Unlike his other arranging activities, in this work Raff's sole aim was to educate and enrich audiences and performers. His attitude is exemplified by his comments about the Chaconne which Raff, along with many of his contemporaries, assumed to be an reduction by Bach himself of an orchestral work: "The purpose of the present treatment, which makes no other claim to merit, is to draw out the polyphonic voices that must have lain in the original setting of the Chaconne ... and to encourage in modern orchestras the confidence to attempt works of this character".