 Despite his seclusion from society , this period saw the composition and publication of many of Alkan 's major piano works , including the <unk> études dans tous les tons mineurs , Op. 39 ( 1857 ) , the Sonatine , Op. 61 ( 1861 ) , the 49 Esquisses , Op. 63 ( 1861 ) , and the five collections of Chants ( 1857 – 1872 ) , as well as the Sonate de concert for cello and piano , Op. 47 ( 1856 ) . These did not pass <unk> ; Hans von Bülow , for example , gave a laudatory review of the Op. 35 Études in the <unk> Berliner <unk> in 1857 , the year in which they were published in Berlin , commenting that " Alkan is <unk> the most eminent representative of the modern piano school at Paris . The virtuoso 's <unk> to travel , and his firm reputation as a teacher , explain why , at present , so little attention has been given to his work in Germany . " 
