A viola concerto is a concerto contrasting a viola with another body of musical instruments such as an orchestra or chamber music ensemble. Throughout music history, especially during the Baroque, Classical, and Romantic eras, viola was viewed mostly as an ensemble instrument. Though there were a few notable concertos written for the instrument in this time period, these instances were quite rare and the instrument continued to be ignored. However, during the 20th century, the instrument was revitalized thanks to the work of a number of violists and composers, which led to the commission and composition of many more viola concertos, expanding the repertoire significantly.