The Complete Idiot''s Guide to Music Theory

Part 3:
Tunes
150
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Mass
A vocal work based on the Roman Catholic mass. The five pas-
sages of the mass that are frequently set for choir or for choir and vocal
soloists include the 
Kyrie
(“Lord have mercy”), 
Gloria in excelsis Deo
(“Glory be to God on high”), 
Credo
(“I believe”), 
Sanctus
(“Holy, holy”),
and 
Agnus Dei
(“O Lamb of God”).
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Minuet
A minuet is a French dance in triple time (3/4, 3/8, 6/8, and so
forth).
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Motet
The motet is a short unaccompanied choral work, popular from
the thirteenth through the sixteenth centuries. The early motet was exclu-
sively a sacred form, based on pre-existing melodies; other words and
melodies were added in counterpoint.
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Opera
An opera is a long, complex dramatic work, incorporating both
voices and instruments. You can think of an opera as the classical equiva-
lent of today’s popular musicals, mixing music with a dramatic plot.
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Operetta
Literally, a “little opera.” More commonly, a shorter or less
ambitious stage work than a full-blown opera, typically with just a single act.
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Oratorio
A dramatic musical setting of a religious libretto, for solo
singers, choir, and orchestra. An oratorio is like a non-secular opera, but
without the scenery or costumes; oratorios are typically performed in con-
cert halls or churches.
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Plainsong
Plainsong, also known as 
plainchant
, is chant comprised of a
single line of vocal melody, typically unaccompanied and performed in the
free rhythm of the spoken word. The form matured during the sixth cen-
tury, at the request of Pope Gregory I, and was subsequently known as
Gregorian chant
.
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