Louis Couperin (1626–1661) was a French Baroque composer from the famous Couperin family. The most well-known member of the family was François Couperin, the son of Louis’s younger brother. Louis Couperin was an organist and harpsichordist and worked at the famous St. Gervais Church; he was also a violist at the French court. Unfortunately, his life was cut short at the age of 35. None of Couperin’s music was published during his lifetime, but manuscript copies of about 200 pieces survive, some of them only rediscovered in the mid-20th century. His innovations in organ music included composing pieces for specific registrations, and in harpsichord music he invented the genre of the unmeasured prelude (prélude non mesuré), for which he devised a special type of notation – the score only determines the pitches but leaves the time signature and rhythm unspecified and up to the musician to decide (one can find similarities with 20th century aleatoric music). This genre remained a peculiarity of the French Baroque and was used very little elsewhere.