Solo harpsichord compositions included dance suites, fantasias, and fugues. Albums include the 24 Preludes and Fugues Op. Domenico Scarlatti has only a few fugues among his corpus of over 500 harpsichord sonatas. Krieger's contemporaries praised his contrapuntal skill, evident in the extant fugues and ricercars. Some fugues during the Baroque period were pieces designed to teach contrapuntal technique to students. Felix Mendelssohn wrote many fugues inspired by his study of the music of J.S. Bach. Sorabji's fugues, the most atonal of his works, generally follow traditional methods. The Magnificat Fugues were all composed during Pachelbel's final years in Nuremberg. These compositions are called the riddle fugues (or sometimes, more appropriately, the "riddle canons"). Invertible counterpoint is essential to permutation fugues but is not found in simple fugues. Pachelbel wrote more than one hundred fugues on free themes. Mozart then set to writing fugues on his own, mimicking the Baroque style. The third movement's structure alternates two slow "arioso" sections with two faster fugues. During his early career in Vienna, Beethoven attracted notice for his performance of these fugues. The panel expressed great displeasure at the dissonance in some of the fugues.