It is interesting to realise that in the 19th century not all pupils of a conservatoire necessarily had to become a ‘professional musician’. Even more, they were considered “as potential members of an audience whose taste and listening habits needed to be educated and refined”, and that at the end of the 19th century “the good will of audiences could no longer be taken for granted: the language of music was moving away from traditional patterns of listening, and when professional musicians [like D’Indy] realised they might lose their listeners, they started to take urgent steps to raise awareness through practical training” (Fend, Noiray 2005:9). In this light, we could also understand Orefici’s proposal to have a more inclusive view on music education “to the widest number of possible users”. Orefici’s ideal has not been realised in Italy, despite the support of important musicians of the time like Toscanini. The situation was rather the contrary since there was a strong opposition led by the then director of the Conservatoire of Florence, Illdebrando Pizzetti. He advocated for a highly technical music education (Caprioli 2017:176), comparable to the kind of music education that most conservatories strived and strive for in the 20th and 21st centuries. The disconnection between a professional- and amateur community had its price, and alienated contemporary music from the “potential members of an audience”. There have been several other ways to educate amateur musicians in the 20th century, but despite the efforts made to engage the public with the latest music, this project can, from a 21st century perspective, be considered a failure. Most 20th century music has only a small club of fans, and even the compositions that are considered ‘masterworks’, a problematic term in itself, are seldom performed. It is not the progressive music of Schoenberg, Stravinsky, Bartok, Boulez or Ligeti that we see regularly on concert-programs, but if there is a 20th century work next to 18th and 19th century repertoire, it is often a work of conservative composers like Shostakovich, Sibelius, John Adams or Strauss. 
The decrease in popularity of contemporary music since the turn of the 20thcentury, has had its effect on the education within conservatoires. Since then, most teachers (instrumental and theory teachers alike) were able to analyse the harmony of a Beethoven composition, but just a few of them understand which grammar Bartok is using in his music, let alone Feldman or Ligeti. The fact that 20th century music is not as successful as the music of the centuries before, makes it less urgent to teach and study this repertoire at a conservatoire. Because where and when can you perform this music? Hence a deadlock for music-theoretical literature is not an issue for most conservatoire staff, since the focus is on the common practice. However, they are happy with any new perspective on old repertoire. A good example of this is the eagerness with which the 'new' partimento discoveries are brought in, translated into new ways of analysing existing repertoire or into new ways of shaping harmony education . These books form a big contrast with literature that tries to shed new light on 20th century repertoire that is mostly missed by most music theory teachers .
Let us go back to the question posed at the end of the introduction: why were pedagogical textbooks used within the conservatoire until halfway the 19th century dealing with the musical vocabulary of its time or its recent history, and after this become victim of a deadlock, a standstill?
I have explored three reasons. First of all, the textbooks that were being used until the 19th century were in fact not music theory textbooks, meant to teach music theory as an independent discipline, but textbooks that were being used to learn the concepts for composition. Therefore, I would propose to not call them music theory books, but composition textbooks. It remains the question how in a 19th century conservatoire, an average instrumentalist was theoretically trained. I will make a start with exploring this in the next chapter. Secondly, in the 19th century the basis of compositional style changed dramatically from a mostly diatonic tonal basis in the previous centuries to a chromatic basis. It seemed difficult to take this chromatic basis as a pedagogical starting point, so textbooks still had to begin with diatonic situations, which automatically meant a reference to examples from before the mid-19th century. In the 20th. century, the problem increased because the basis of compositional styles changed even more radically, and we see a development towards increasingly individualistic and ideosyncratic styles. This made it difficult to create a method based on common principles. Thirdly, the musical developments in the 19th century led to a division between amateur and professional musicians, with the almost complete isolation of contemporary composed art music during the 20thand 21st centuries as a result. Because of this, the urge to study contemporary music at a conservatoire became very low, which is still the case today.
Until now, I focused primarily on what is being seen as the core of music-theoretical literature, which turns out to be in fact compositional literature. The question arises: how could we define specific (or typical) non-compositional music-theoretical training?
It would be interesting to travel back in time and see what kind of ‘theoretical knowledge’ or specific skills (like improvising) an average 17th century singer in one of the many churches in Napoli would have, or a trumpet player in one of the Parisian theatres at the beginning of the 19th century, or a young pianist around 1900…
 I would like to sort this out more precisely. As Paul Craenen said rightfully: ‘some works have a better press, than others, think for instance of The rite of Spring in comparison to the works of Schönberg’.
 see for ex. IJzermann’s new book Harmony, Counterpoint, Partimento: A New Method Inspired by Old Masters. Oxford: Oxford University Press 2019
 ex. Wünsh Satztechniken im 20. Jahrhundert. Kassel: Bärenreiter-Verlag 2014.