Some of Alkan 's music give hints of the obsessiveness which some have detected in his personality . The Chant Op. 38 , no . 2 , entitled Fa , repeat the note of its title incessantly ( in total 414 times ) against shifting harmonies which make it " cut ... into the texture with the ruthless precision of a laser beam . " In modelling his five sets of Chants on the first book of Mendelssohn 's Songs Without Words , Alkan ensured that the pieces in each of his sets followed precisely the same key signatures , and even the moods , of the original . Alkan was rigorous in his enharmonic spelling , occasionally modulating to keys containing double @-@ sharps or double @-@ flats , so pianists are occasionally required to come to terms with unusual keys such as E @-@ sharp major , enharmonic equivalent to F major , and the occasional triple @-@ sharp .