One Voice Per Part - this musical term and neologism and its abbreviation refers to the practice of performing Baroque choral music, and Bach's works in particular, with single voices on each vocal line. Choral works featuring SATB (soprano, alto, tenor and bass) vocal parts are consequently sung by four singers when this approach is adopted.
The first conductor to strongly advocate this approach to the music of Johann Sebastian Bach was the American pianist and conductor, Joshua Rifkin. The use of solo voices in the choral music of Bach has also found champions in Andrew Parrott, Paul McCreesh, Sigiswald Kuijken and Konrad Junghänel. The approach is still somewhat controversial and recordings of Bach's music featuring solo voices in choral movements have met with mixed reviews.
The acronym, "OVPP", was first coined in the egroup "The Bach Recordings Discussion Group" in the mid 1990s by Steven Langley Guy. The acronym seems to have been adopted more widely since that time.