All notes have a duration in time,
but in western musical notation,
the duration is expressed as fractions or
multiples of a beat,
rather than as a duration in seconds.
Beats are related to or
even synonymous with pulse.
And they're clearly related to tempo,
which is often expressed
as beats per minute.
Rhythm then concerns multiples or
subdivisions of beats.
It can be expressed symbolically
in western notation
in the form of both rests and notes.
So for instance,
all of our western rhythmic durations
are related to the whole note,
as it's called in America, or
the semibreve, as it's called in Britain.
Semibreve represents the full
duration of one bar in 4/4 meter.
We'll come to meter in a little while, but
suffice to say, 4/4 is the most
common meter that we come across.
The semibreve can,
of course, be subdivided and
these subdivision have different names.
In British nomenclature, for example, we
speak of minims, crotchets, quavers, etc.
There are two minims per semibreve.
This is also known as the half
note in American parlance.
This is then subdivided
into two crotchets,
crotchets are quarter notes in the US and
there are four quarter notes in a whole
note, or a semibreve as you might imagine.
Crotchets are then further divided
into quavers, eighth notes, and
on into semiquavers, 16th notes,
and so on and so forth.
So if you use the American nomenclature,
which is derived from the German,
by the way, it's very easy to see how
many of a particular rhythm you'll
have in a whole note, as all rhythms
are expressed in relation to this.
So let's just recap here and look at
the actual notation of these rhythms.
First of all,
we've got the open round note symbol,
which is the semibreve or whole note.
This is four beats long in common time,
or 4/4 meter.
Again, more on this later.
Then we've got the half note, or
minim, the crotchet, the quaver,
and the semiquaver.
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We also have the equivalent
rhythms in rests.
Rests are necessary to indicate where
a musician stops playing notes.
Most music consists of notes surrounded
by space, of course, otherwise musicians
would never get the chance to breathe or
rest, and neither would the music.
So first of all, again, the semibreve or
whole note rest, the minim or
half note rest, the crotchet or
quarter note rest, the quaver,
eighth note rest, and the semiquaver,
or sixteenth note rest.
You can see that the quaver and
semiquaver notes are essentially crotchets
with little flags on their stems.
Each flag that you add
divides the rhythm by two.
So we could further divide
semiquavers into demisemiquavers or
32nd notes in American parlance.
And these can be further subdivided
into hemdemisemiquavers or 64th notes,
etc., etc.
Now those flags, which we've seen
on the quavers of lesser durations,
can actually turn into what we call beams.
We use beams so that we can group
notes in twos, fours, eights, etc.
And thereby easily see a beat's worth,
or sometimes more, of shorter notes.
This makes it easier to orientate
ourselves in the flow of the music, so
we can recognize where
the beat boundaries are.
Here's another example.
You can see that the number of flags
which we use in the individual notes
is reflected in the number
of horizontal beams.
And that adding one more beam is
equivalent to adding one more flag,
that is,
we're subdividing the rhythm into two.
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