ALESIS SR-16 - Manual (Page 65)

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8.4 UNDERSTANDING RHYTHMIC NOTATION
Measures A piece of music is divided into smaller units called measures (also called bars),
and each measure is divided into beats. In the SR-16, each beat is further sub-divided into 96
sub-beats.
Rhythmic Values for Notes With a measure written in a 4/4 time signature, there are 4
beats per measure, and each beat represents a quarter (1/4) note. Thus, there are 4 quarter
notes per measure of 4/4 music. With a 3/4 time signature the "numerator" indicates that there
are 3 beats per measure, while the "denominator" indicates that each of these beats is a
quarter note (1/4).
There are two eighth notes per quarter note. Thus, there are eight eighth notes per measure
of 4/4 music.
There are four16th notes per quarter note. Thus, there are sixteen 16th notes per measure of
4/4 music.
There are eight 32nd notes per quarter note. Thus, there are thirty-two 32nd notes per
measure of 4/4 music.
There are also notes that span a greater number of beats than quarter notes. A half note
equals two quarter notes. Therefore, there are two half notes per measure of 4/4 music. A
whole note equals four quarter notes, so there is one whole note per measure of 4/4 music.
(We keep referring these notes to 4/4 music because that is the most commonly used time
signature in contemporary Western music.)
Triplets The above notes divide measures by factors of two. However, there are some
cases where you want to divide a beat into thirds, giving three notes per beat. Dividing a
quarter note by three results in eighth-note triplets. The reason why we use the term eighth-
note triplets is because the eighth note is closest to the actual rhythmic value. Dividing an
eighth note by three results in 16th-note triplets. Dividing a 16th note by three results in 32nd
note triplets.
Rests You can also specify where notes should not be played; this is indicated by a rest,
which can be the same length as any of the rhythmic values used for notes.
Dotted Notes and Rests Adding a dot next to a note or rest means that it should play
one-and-one-half times as long as the indicated value. This of course does not apply to
percussion parts. Example: A dotted eighth note would last as long as three 16th notes (since
an eighth note is the same as two 16th notes).
Uncommon Time Signatures 4/4 (and to a lesser extent 3/4) are the most common time
signatures in our culture, but they are by no means the only ones. In jazz, both 5/4 (where
each measure consists of five quarter notes) and 7/4 (where each measure consists of seven
quarter notes) are often used. In practice, complex time signatures are played like a
combination of simpler time signatures; for example, some 7/4 compositions would have you
count each measure not as 1, 2, 3, 4, 5, 6, 7 but as 1, 2, 3, 4, 1, 2, 3. It's often easier to think of
7/4 as one bar of 4/4 followed by one bar of 3/4 (or the other way around, depending on the
phrasing), since as we mentioned, 4/4 and 3/4 are extremely common time signatures.