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Lesson 6: Constant versus changing time, adding triplets, and duplets

Video transcript

at times especially in popular dance forms the meter will remain constant all ballroom dancing fits into this category a March would also fit into this category remaining constant usually in 2/4 it is also the case with most music from the 18th and 19th centuries in the latter part of the 1800s and into the 1900s composers started to feel free to change meters during a movement or work sometimes quite often the actual meters remain as we have discussed if we look at the last movement of the Sam Jones cello concerto we can see some simple changes of meter from 2 4 2 3 4 back 2 2 4 then 3 4 & 4 4 another simple example is in Philip Glass's harmonium mountain and this excerpt he mixes the metres 2/4 3/4 and 4/4 if we look at david stocks work called blasts written in 2010 we find a more complicated section of meter changers using 5 8 7 8 3 4 & 4 4 if we look at a 4/4 measure we have learned that the measured can easily be divided by using various note lengths half notes quarter notes sixteenth notes thirty-second notes and so forth but what if a composer would like to divide one of those quarter notes into three equal parts to create more rhythmic interest we accomplish this by adding a three above or below a group of three eighth notes the three signifies that three notes are performed during the time of one quarter note let's again look at Philip Glass's harmonium Mountain in this passage we see the violins playing the groups of three called triplets and the violas and cellos are playing quarter notes then the violas joined the violins playing triplets the cellos play the eighth notes and the double basses play the quarter notes this method of changing tuple notes to tripple notes can work in any duple meter the composer can also divide the triple bead in different ways for example instead of three eighth notes in a beat we could see an eighth note in a quarter note or a quarter note and an eighth note we still need the number three above or below the notes if you look at revel status and Chloe the meter is five four but Ravel adds the three for each part to create triplets you will see that he doesn't continue to write the three during the continuation of the excerpt assuming that the performer understands the pattern the triplet is the most common variation within a meter but there could also be for example five notes within a quarter again with a five above or below or six or quite frankly any number that is not common to the meter in a triple meter like 6/8 one could do the same 6/8 can be one dotted half note or two dotted quarter notes or six eighths or 1216 we could also have a rhythm of quarter eighth or eighth quarter or any combination that adds up to six eighth notes if the composer wanted four notes during a dotted quarter note the number four would go above or below the group of notes as you can see the notation of rhythm can become very complicated we will discuss this in later lessons you