Nicola Antonio Porpora, an Italian composer of the Baroque era, is perhaps best known for his contributions to opera. However, your mention of "Solfeggio" refers to a different aspect of music education. Solfeggio is a vocal exercise that uses solmization syllables to teach pitch and sight-singing. Porpora's work in this area is not as widely recognized as his operatic compositions, but he did contribute to vocal pedagogy.
Porpora wrote a treatise titled "Solfeggiamento," where he discussed the application of solfeggio in vocal training. He emphasized the importance of mastering solfeggio as a fundamental skill for singers. While his fame primarily lies in his operatic works and his role as a teacher of many prominent singers of his time, his contributions to the development of vocal technique, including solfeggio, showcase his influence in music education.