Alexander Robert Reinagle (23 April 1756 – 21 September 1809) was an English-born American composer, organist, and theater musician. He should not be confused with his nephew of the same name, Alexander Robert Reinagle (21 August 1799 — 6 April 1877), also a composer and organist, who lived all his life in Britain.
His earliest compositions, from his days in Edinburgh, include a set of Duos for two ‘cellos, Opus 2, and Variations on Famous Scots Tunes, published in Glasgow and later in Philadelphia. He also composed Twenty-four Short and Easy Lessons, a series of teaching pieces for keyboard, which he later used in his teaching in Philadelphia.
Once in America, Reinagle continued to compose short pieces for special occasions, often with titles alluding to American personalities and ideas. Pieces such as his Federal March, President Madison’s March and Mrs. Madison’s Minuet are usually short and in the binary form associated with dance music of the time. Of more interest is the set of four keyboard sonatas. Reinagle composed these when he first arrived in Philadelphia; hence they are sometimes called the “Philadelphia Sonatas”. These are the first sonatas composed in the United States. They are substantial works, each in two or three movements. While they show the influence of C. P. E. Bach (one of Reinagle's idols), they demonstrate Reinagle’s unique approach to form and motivic development.