plainsong

• plain song, plain-song

plain +‎ song, calque of Latin cantus planus.

plainsong (countable and uncountable, plural plainsongs)

1. (music) A form of monophonic chant in unison using the Gregorian scale, sung in various Christian churches.

   Synonym: plainchant

2. (music) A cantus firmus or theme chosen for contrapuntal treatment; so called because often an actual fragment of plain-song.
3. (music) The simple notes of an air, without ornament or variation.
4. (by extension) A plain unvarnished statement, without exaggeration.

• Gregorian chant

• “plainsong”, in The Century Dictionary […], New York, N.Y.: The Century Co., 1911, →OCLC.

• planigons, pangolins