Carlos Seixas, full name José António Carlos de Seixas, was a distinguished Portuguese composer born on June 11, 1704, in Coimbra, Portugal, and passed away on August 25, 1742, in Lisbon. Acclaimed for his virtuosity as a harpsichordist and an organist, Seixas was a prominent figure in the Portuguese Baroque era, contributing significantly to the musical landscape of the 18th century. He was the son of the cathedral organist Francisco Vaz and Marcelina Nunes.

Despite his short life, Seixas left behind an extensive body of work, including over 700 compositions, although many have unfortunately been lost. He composed mainly keyboard music, which included sonatas that showcase his mastery of the instrument and his Iberian heritage. These sonatas display a variety of affects, ranging from the gallant style to more intricate counterpoint, revealing the evolution of music from the Baroque to the Classical period. Seixas also composed vocal religious music, reflecting his position as the organist at Lisbon's cathedral and later at the Royal Chapel, a role he took up after his father. Seixas’s legacy is captured in the recordings and performances of his sonatas and toccatas that continue to be admired and studied for their technical brilliance and expressive depth.