Busoni wrote a number of essays on music. The "Entwurf einer neue Ästhetike der Tonkunst" ("Sketch of a New Esthetic of Music"), first published in 1907, set out the principles underlying his performances and his mature compositions. A collection of reflections which are "the outcome of convictions long held and slowly matured", the "Sketch" asserts that "The spirit of an artwork ... remains unchanged in value through changing years" but its form, manner of expression, and the conventions of the era when it was created, "are transient and age rapidly". The "Sketch" includes the maxim that "Music was born free; and to win freedom is its destiny". It therefore takes issue with conventional wisdom on music, caricatured by Busoni as the constricting rules of the "lawgivers". It praises the music of Beethoven and JS Bach as the essence of the spirit of music ("Ur-Musik") and says that their art should "be conceived as a "beginning", and not as an unsurpassable finality." Busoni asserts the right of the interpreter vis-à-vis the purism of the "lawgivers". "The performance of music, its "emotional interpretation", derives from those free heights whence descended Art itself ... What the composer's inspiration "necessarily" loses through notation, his interpreter should restore by his own." He envisages a future music that will include the division of the octave into more than the traditional 12 semitones. However, he asserted the importance of musical form and structure: His idea of a 'Young Classicism' "aimed to incorporate experimental features in "firm, rounded forms" ... motivated each time by musical necessity." (Brendel).