Jaak Nikolaas Lemmens (1823–1881) was a Belgian composer, music educator, and organist, known for his significant contributions to organ music and his role in music education. He primarily composed in the Romantic genre and is recognized for his innovative compositions that expanded the technical and expressive capabilities of the organ. Lemmens studied under notable musicians, including the renowned organist and composer, Franz Liszt. His notable works include "Symphonie No. 1," "Six Pièces," and various organ pieces that are still performed today. He was particularly known for his pedagogical approach to organ playing, which influenced a generation of organists. His impact on music is evident in his ability to bridge the gap between traditional organ music and the emerging Romantic style, fostering a greater appreciation for the organ as a solo instrument. Lemmens also played a crucial role in developing music education in Belgium, establishing the foundations for future generations of musicians. His legacy endures in the repertoire of organists and through his influence on music pedagogy.