[BLANK_AUDIO] All notes have a duration in time, but in Western musical notation the duration is expressed as a 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 notations are related to the whole note, as it's called in America, or the Semibreve, as it's called in Britain. Semibreve represent the full duration of one bar in 4/4 meter. We'll come to meter in a little while, but suffice it to say, 4/4 is the most common meter that we come across. The Semibreve, can of course be subdivided, and these subdivisions 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 U.S., 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, Sixteenth 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 will 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 four, four meter, again more on this later. Then we've the half note or minim, the crotchet, the quaver and the semiquaver. 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 change 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 hemidemisemiquavers, or 64th Notes, etcetera, etcetera. Now those flags which we've seen on the quavers and lesser durations, can actually turn into what we call beams. We use beams so that we group notes into twos, fours, eights, et cetera, 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 the equivalent to adding one more flag. That is, we're subdividing the rhythm into two. [BLANK_AUDIO]
