Charlotte & Josefien Stoppelenburg (alto/mezzo-soprano and soprano) form the singing duo Unique Harmony of Two Voices. In 1997, the sisters were the first to win the Princess Christina Competition for vocalists. Television appearances (Queens Day 2002, Una Voce Particolare) have made their interpretation of the Flower Duet (from the opera Lakmé by Leo Delibes) well-known in their country, but they also regularly performed abroad (for example in Germany, United States, South Africa and Venezuela). The exceptional way their voices blend, perfected by outstanding individual technique and years of experience together has enabled them to reach a large audience. The sisters frequently perform as soloists with various ensembles: piano, chamber- and symphonic orchestra, choir or instrumental ensembles. They are familiar with the repertoire of Lied, oratory and opera and are especially passionate about contemporary music. Various Dutch and German composers have written or arranged specially for them. Charlotte and Josefien are frequently asked to perform during festivities, whether for business firms or private persons.