Music Theory 101 Question

[gregdidge]

I just downloaded a tune that I wanted to learn. It was an hymn written in 4 flats. I had no idea what key it was written in. The lowest note was one note too low for a normal D tune. The software that would open the file and display the score could transpose it but it wanted to know how many semitones I wanted to move. By trial and error I found out that the correct number was 6. That gave me the tune in 2 sharps and the correct range. So now the question is what is the relation of a semitone to a tone? I would like to know why what I did worked.

Thanks! Greg

[blackhawk]

Not that I can answer a question like that, but out of curiousity, which hymn was it?

[Crysania]

Well, without seeing the music it will be tough to figure out exactly what key. But my guess is that it was in Ab major. Moving up 6 semitones from Ab major would get you D major (which as 2 sharps), so I'm going to hazard a guess that that is the right key.

As for semitone vs. tone. A "semitone" is between adjacent half-steps on the piano (i.e. one white key and a black key; or the two white keys next to each other without a black key in the middle). A "tone" is equal to two semitones (so D to E is a tone).

We also refer to them as a halfstep (semitone) and step (tone).

I hope that helps a bit!

~Crysania

[gregdidge]

How wonderful (I stand amazed in the presence of Jesus the Nazarene)

[falkbeer]

There are 8 notes in the western diatonic scale. But it is really made up of only 7 notes: C-D-E-F-G-A-B-(C) this ofcourse you alredy know! there are generally two semitones to between the steps in the scale, exept for E-F, and B-C, which are half tone steps (semitones)

However from a practical point of view one could argue that the western scale really is a twelve tone (semitones) scale consisting of the notes:
C-C#(Db)-D-D#(Eb)-E-F-F#(Gb)-G-G#(Ab)-A-A#(Bb)-B,
where C#=Db

In musical theory it is customary to arrange these tones in The Circle of Fifth. It´s very important concept in musical theory. But it helps very much in understanding harmony and the relationship between keyes.
The 12-tone scale arranged in the circle of fifth: C-G-D-A-E-B-Gb-Db-Ab-Eb-Bb-F-C

Studying musical theory is very rewarding and it certanly will make your understanding of music deeper, epecially if you are interested in classical music.

Good luck!

[Martin Milner]

Crysania is spot on, Ab Major.

Here's the circle of fifths. You know D major is two ##s and G Major is noe # and C major is no #s. F Major is one b, Bb major 2 flats, Eb Major is three flats and Ab major four flats.

Two semitones = one tone.

You can learn more on Wikipedia here:

http://en.wikipedia.org/wiki/Category:Musical_keys

[MTGuru]

The easy rule of thumb is that when you see a key signature with multiple flats, the second to last flat is the major key. So with 4 flats you have: Bb Eb Ab and Db. The second to last here is Ab, so that's the key.

When there's only one flat, Bb, the key is F. You just have to know that.

A semitone is the same as a half-step, the difference between two consecutive notes of the chromatic scale. So to get from Ab to D, you have to count up the notes of the chromatic scale: Ab A Bb B C Db D. Counting the intervals, you get Ab to A is 1 semitone, A to Bb is another semitone, etc. By the time you get to D, you should have counted 6 semitones. So that means that D is 6 semitones higher than Ab. That's why your transposition worked!

Of course, you can also count down: Ab G Gb F E Eb D. That give you 6 semitones lower from Ab to D -- which happens to be the same number in this case, but won't always be. This will also put you in D, but an octave lower than when you count up.

Also note that it doesn't matter if you count chromatically by sharp or flat notes. For example, since Ab is the same as G#, you could count up: G# A A# B C C# D. You still get the same result of 6 semitones.

BTW, the rule for sharp keys is also easy. When you see multiple sharps, look at the last sharp, and raise it one semitone, and that's your major key. So with 2 sharps you have: F# C#. Raise the C# a half step, and you get D. Voilà, that's your key. With three sharps: F# C# G#, raise the G# a half step to A. And so on.

Note to other chiffers: Yes, enharmonic notes are the "same" only in 12TET tuning. Trying to keep things simple here.

Edited to add: I see there were 3 other posts while I was writing this! I agree, the cycle of fifths is also good to know, once you're comfortable with the scales and intervals.

[lalit]

Note to other chiffers: Yes, enharmonic notes are the "same" only in 12TET tuning. Trying to keep things simple here.

Thank you. --Adoring fan of different temperaments.

[gregdidge]

What has been said makes sense to me. (I think) BUT why is it that I transposed the tune up by 6 semitones and the lowest note in the tune only moved up 1 note? I would think it should've moved up three notes. (there I go thinking again) If this is getting in too deep thats OK. I'm just curious.

[Crysania]

All of the notes should have moved up 6 semitones. It sounds like you didn't transpose the whole thing correctly. The Db on the bottom should have become F#.

We could help out more if you could let us know what tune it is you're trying to play or scan in the original music so we can see it.

~Crysania

[FJohnSharp]

http://www.teoria.com/reference/scales/05.htm

[Brian Boru]

Crysania is spot on, Ab Major.

Here's the circle of fifths. You know D major is two ##s and G Major is noe # and C major is no #s. F Major is one b, Bb major 2 flats, Eb Major is three flats and Ab major four flats.

Two semitones = one tone.

You can learn more on Wikipedia here:

http://en.wikipedia.org/wiki/Category:Musical_keys

If this is any help I always remember the circle of fifths as "Father Charles Goes Down And Ends Battle". This works for sharps and for flats you say the phrase backwards.

[fel bautista]

Thanks for this post. I get corn-fused as well. So how do modes relate to keys??

[MTGuru]

Thanks for this post. I get corn-fused as well. So how do modes relate to keys??

Sorry, Fel, that's Music Theory 102. Oh, OK ...

For a given major key, call it the base key, the mode is the scale that begins on one of the diatonic scale tones of the base key, and using only diatonic tones of that base key. So for the base key of C major, the related modes are the "white key" scales starting on:

C (+0) - Ionian (Major)
D (+1) - Dorian
E (+2) - Phrygian
F (+3) - Lydian
G (+4) - Mixolydian
A (+5) - Aeolian (Minor)
B (+6) - Locrian

The base key determines the key signature for all its related modes. So all the modes based on G major will have one sharp (F#); all the modes based on F major will have one flat (Bb), etc.

Conversely, if you're in, say, G Dorian, the chart tells you that you're +1 from the base key. You need to count down -1 to get to the base key. One down from G is F. So the base key is F major, and the key sig is one flat. Another: if you're in A Mixolydian, you're up +4. Count down -4 from A and you get to D. So the base key is D major, or two sharps. And so on.

[markbell]

Greg,

I pulled the same hymn down from cyberhymnal. It is written in A-flat, with 4 flats, and therefore unplayable on a D whistle. As you discovered, a transposition up 6 semitones, puts it beautifully in whistle range for D.

However, the lowest note in the A-flat version is C, and the lowest note when transposed is F# - I think you might have missed something.

Just to bend the synapses, if you transpose down 6 semitones, you'd also get the key of D, but an octave too low for the soprano whistle. A-flat is exactly half way round the circle of fifths from D.

This is a great tune, and I think I'll add tablature to it and post it on my website!

Mark