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Lesson 8: Natural sign, more on accidentals and key signature

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- [Instructor] The sign for a natural looks like this. If a note does not have a flat or sharp before it, it is always a natural, with two exceptions. The first exception is, when an occidental is placed before a note, that note will always sound that way through the entire bar. (simple piano notes) Once the bar line appears, the note will return to a natural, unless the occidental, sharp or flat, is added again. (simple piano notes) Let's look at the last movement of Beethoven's Fifth Symphony once again. Notice the F sharp in the second bar on this excerpt, and that after the bar line, the sharp needs to be added again. In the fourth bar of this excerpt, we notice that the F sharp carries through the bar. ("Fifth Symphony" by Beethoven) The second exception is what is called a key signature. A key signature is a sharp or a flat, or multiple sharps or multiple flats, that are placed at the beginning of a line of music, between the clef and the time signature, and then, at the beginning of the line of music following. For an example, let's add one sharp to the key signature. First the staff, then a clef, let's use a treble clef, then a single sharp, and then the time signature, let's use four four. The first sharp is always an F, and, in treble clef, it's placed on the top line, the fifth line. In a bass clef, the first sharp is placed on the fourth line. The result is that any time a F is played anywhere in this piece, the F will be altered to a F sharp. Let's play four F's, two in the bass clef, (simple piano notes) and two in the treble clef. (simple piano notes) Now we add a sharp sign to the beginning of the staff and all of the F's now become F sharps. (simple piano notes) Let's look at one flat in the key signature. The first flat is always a B. In treble clef, it's on the third line. In bass clef, it's on the second line. Again, that means that every B written will be a B flat, without the need to add the flat sign before the note again. It's important to learn that if we have sharps in the key signature, we cannot also have flats in the key signature. If we have flats in the key signature, we cannot also have sharps in the key signature. If we are playing a work with one sharp in the key signature, of course, we know that sharp is always an F, but the composer would like to have a F natural played, a natural sign would have to be placed before the F. Let's look at the oboe part during a section of the Brahm's Academic Festival Overture. We first notice that Brahms writes a sharp sign at the beginning of the line on the fifth line in treble clef. Of course, we know also that that indicates that all F's are now F sharps. Since Brahms wants a F natural in this bar, he has to add the natural sign. He also does this in the first violin part. ("Academic Festival Overture" by Brahms) The same applies to flats. Let's look at Tchaikovsky's "Fourth Symphony", last movement. Notice that the first flat is always a B, and in treble clef, it comes on the third line. In the melody played by the flute, Tchaikovsky wants a B natural, rather than a B flat, so he must put a natural sign in front of the B. ("Fourth Symphony" by Tchaikovsky)