Joseph Joachim Raff was born on 27 May 1822 in the small town of Lachen, on the shores of lake Zürich in Switzerland. He was a good violinist, but only a competent pianist and by no means a virtuoso, although he had given a couple of recitals whilst in his early 20s in Switzerland. He didn't compose at the piano either, preferring to use it only to check a passage once he had composed it. Nonetheless, his first 59 compositions were for the piano and he continued to write many pieces for the instrument even once he had established his reputation in much larger forms. By a large margin, Raff wrote more music for solo piano than for any other medium.

By 1868, the year in which he composed the first of the pieces which were eventually going to become his Dreizig fortschreitende Etüden WoO.36 (Thirty Progressive Etudes), Raff's career was taking off. His First Symphony had won a major prize and received great acclaim, his chamber and choral works were attracting attention and he seems to have had no difficulty in attracting publishers. Yet despite this success he was still working as a teacher and a critic and it was still necessary for him to write popular piano pieces to keep money flowing into the household. He was a born educator; for many years he taught piano at two girls schools in Wiesbaden and later his composition class at the Hoch Conservatory in Frankfurt was greatly admired. He also had a ready pen, writing music criticism through his life until he took up the Frankfurt post. It is surprising, therefore, that he never wrote a musical textbook of any sort and his piano etudes are for the most part wholly artistic in conception and not intended as pianistic exercises.

During Raff's lifetime, the thirty etudes were spread over Damm's three books in their three editions. Whilst Raff no doubt thought of the first 27 as a coherent set, as they appeared together in the second edition of the Übungsbuch, it's not known whether he felt that the final three, published earlier in the Kunstfertigheit should also belong to the set. In any event, just a year after Raff died, and having in the meantime shed his pseudonym and set up his own publishing house, Steingräber published the complete set as 30 Progressive Etudes in October 1883. Clearly the title was not Raff's, although it is appropraite. The set is "progressive" not so much in the difficulty of each work, but in the move from the more straightforward, focussed exercises of the first fifteen to the employment of the techniques learned from them in the larger, more developed and artistically richer works which particularly characterise the final ten pieces.

Source: Raff.org (https://www.raff.org/music/detail/piano/30prog.htm).
Although originally created for Piano, I created this Interpretation of the Allegro from 30 Progressive Etudes (WoO. 36 No. 25) for String Quartet (2 Violins, Viola & Cello).