[MUSIC] In the last lecture, I talked about meter being created by a regular pattern of accents, with accents being defined as anything that makes a note more noticeable, such as being louder, softer, higher, lower, or longer than its neighbors. Accents create beats on multiple levels at various speeds. The beat that we naturally tap or move to can be called the meter beat, the tactus, or the macrobeat. Every meter beat level is subdivided by faster levels. We label the meters based on the value of the meter beat and the number of subdivisions found in each beat. I can demonstrate using this C minor prelude from the last lecture. At this speed [MUSIC] The most likely meter beat is the quarter note. [SOUND] The quarter note level is shown by the black arrows. The quarter note level can be divided by twos, into eighth notes, which are shown here by the red arrows. [SOUND], the eighth note level can be divided by two In the sixteenth notes, which are shown here by the green arrows. The quarter notes can also be grouped together by twos and a half notes, shown by the blue arrows. [SOUND] Or into whole notes shown by the purple arrow. [SOUND] The beat of each level is twice as long as the beat of the next faster level. There is no beat level that lands itself to grouping by threes. In some meters on the other hand, we can group at least one level into the threes. This is another prelude from the well tempered Clavier, this time in C# major. When you try to keep the beat to this one, you'll either do it once a measure or three times a measure. [MUSIC] Here are the possible beat levels. We either hear the meter beat as the red arrows, at the beginning of every measure, [SOUND] Or we hear it as the green arrows every eight note, [SOUND] Notice that the red arrows fall every three green arrows. Unlike the C minor prelude, this prelude has a triple level, in which beats group by threes. The meter creating accents come mostly from the change of notes at the beginnings of every measure. So, [SOUND] Note changes, [SOUND] That's when the pattern gets broken, at the beginning of every measure, when it changes notes. We show the meter of the music with the meter signature also called the time signature. The bottom number gives us the value of a reference note where 4 stands for quarter note, 8 stands for eighth notes, 2 stands for half notes, and so on. The top number tells us how many of those reference notes fit within each measure. This prelude is in three-eight time which means there must be three-eigth notes in a measure. Here the meter is 4/4, four quarter notes in a measure. There's a beam every 4-16th notes because that's the pattern created by the accents in the music. I could write it in three-eight, grouping 16th notes by 6, but it looks bizarre because it doesn't reflect the accent pattern created by the notes. Compare the top line to the bottom line. Here's the top line, 1 2 3 4 5 6, 1 2 3 4 5 6, 1 2 3 4 5 6, 1 2 3 4 5 6, it's very strange. The numbers don't change at the accent points. But when I do the bottom line, 1 2 3 4, 1 2 3 4, 1 2 3 4, 1 2 3 4, it makes perfect sense. The numbers change where the accents are. When the computer plays it, it sounds exactly the same, in either 3/8 or 4/4. We'd never know it was written in 3/8. Here's the 3/8 version. [MUSIC] It sounds exactly the same. But for human performers, we try to notate the rhythm of the music in such a way that it agrees with the meter being created by the music. If the music has all duple level it makes no sense to notate it with a triple level, as I've done here. In 3/8 we have a conflict of accents. According to the meter signature, the accent should be here. According to the accents created by the high note low note and repeating notes the accents are here So when a performer plays from this notation, the conflict makes it very hard to read and perform the music. Looking at the correct notation, we see the first measure contains 16 16th notes in each staff grouped by fours. Remember that four 16th notes equals one quarter note, so each measure contains the equivalent of four quarter notes as dictated by the time signature. And 4 0 4 means one more thing, eight notes and in fact all levels will be grouped by 2's or 4's. There won't be any triple groupings of anything in 4 0 4. In 4 0 4 Two four, and three four. In fact in any meter in which the number of reference notes in a measure, the top number is two, three, four. Or any multiple of two that is not also a multiple of three. The eighth notes are grouped by 2's or multiples of 2 as are all level below the eight note as shown here. Meters that have no levels of triple grouping are only a single group of three-reference notes in a measure such as three-four or three-eight are called simple meters. These numbers are two, three, and four So they aren't some multiple of three, larger than three, so these are simple meters. We can't form more than one group of three in a measure for any of them. If the tab number is multiple of three, larger than three, such as 6,9 or 12, the reference notes will be group by three. So six eight has two groups of three eighth notes in each measure. Nine eight has three groups of three eighth notes. 12 16 has 12 sixteenths in a measure, arranged in four groups of 3 sixteenth notes, or the equivalent as shown here. Traditionally meters in which there are two or more groups of three reference notes are called compound meters. A meter that has two groups of three per measure, one two three two two three, such as six eight, is called compound duple. A meter that has three groups of three per measure, one two three two two three three two three, such as nine eight, is called compound triple. Notating rhythms can be very challenging. We must do more than simply have the right number of beats in a measure. The notation must agree with the meter that is being implied by the musical accents which are created by various elements in the music. When we notate rhythm in the various meters, we need to show this metric grouping in the notation as much as possible. The most way is by connecting the eighth notes together with beams grouping by 2's or 3's. In the next lecture, I'll go into more detail. [MUSIC]
