concertante
Pronunciation: /ˌkɒntʃəˈtanteɪ, -ˈtanti/
adjective
- 1denoting a piece of music containing one or more solo parts, typically of less prominence than in a concerto: he wrote several concertante worksSee also sinfonia concertante.

Origin:
Italian, 'harmonizing', from concertare 'harmonize'