From 2019 to 2022, Johannes Leertouwer conducted PhD research into 19th-century performance practices of the orchestral music of Johannes Brahms at the Academy of Creative and Performing Arts (ACPA) of Leiden University. In January 2023 he obtained his doctorate. Working with a special Project Orchestra and soloists playing on 19th-century instruments or copies of such instruments, he investigated lost expressive tools of the past in practice as an integral part of his research. Over the course of his research project he has recorded the four Brahms symphonies and the four concertos. Together with his orchestra and the soloists, Johannes has developing a way of handling tempo modifications, vibrato and portamento that resulted in sounding results that differ significantly from any results in both the mainstream performance practice and HIPP of 19th-century repertoire. The audio recordings, that were presented as limited edition Cd-recordings as integral part of his dissertation are available on this website, as is the written part of the dissertation. The process of researching, investigating, developing and implementing lost expressive tools is documented in film and video recordings that can also be found on this page.