[1] Choral works featuring SATB (soprano, alto, tenor and bass) vocal parts are consequently sung by four singers when this approach is adopted.
[2] 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.
[3] Furthermore, the presence, absence and omission of solo and tutti markings in scores, as well as the ambiguity in their meaning, brings further doubt to the question of whether Bach used more than one singer per part or not.
[4] The initialism OVPP was first coined in the Internet mailing list "The Bach Recordings Discussion Group" in the mid 1990s by Steven Langley Guy.