Why use the double flat?

[zac2944]

The music below is a measure from a new tune I'm trying to learn. Why would the Bb be double flatted when you could just write an Ab?



Am I missing something here?

[slybass3000]

The use of the double flat in this example is wrong. It should be an A natural because the movement goes up. There is a rule you can apply: use sharps or natural in this case as accendentals when the the line goes up and use the flats for any accidentals when the line goes down. Be concious about the key signature.

hope this help,

Sylvain

[Mushroo]

Bbb=A, not Ab :-)

My guess is they used Bbb instead of A in that passage because they wanted to make it clear it's the b3rd of Gb, not an augmented 2nd. Personally, I would have used the A since it is an ascending chromatic passage.

[BassChuck]

Well, first of all the Bbb is the same sound as an A natural, so an Ab wouldn't work.

Next, the double flat (in your example) is used to show that the movement of the notes is an upward scale, where using an A natural would not look quite the same. For musicians that are sight reading this can be a help.

Lastly (not in your example) double flats (and double sharps) are used to keep the intervalic sound the same as what is noted on the page. For instance: In the key of G minor, the 3rd note of the scale is a Bb. If we are playing a G minor chord we need to see that the G and the Bb are a third away, this helps in reading and in understanding the harmony. If we are playing in Gb minor (not a common key, but it does happen) the third of the chord is Bbb. When we use the double flat here, we can easily see that the Bbb is the third of the chord and the context of the harmony is easier to see as we read the music.

Its not something that comes up very often. You'll need to be in an uncommon key (lots of sharps or lots of flats) or doing some unusual kind of modulation to really need them.... and in some case (where the above examples are really a concern) the part copier may just use the more common notation.

[zac2944]

Originally Posted by Mushroo

Bbb=A, not Ab :-)

Hmm. Well there's one of my problems. I thought that since the B is Bb due to the key signature, then putting two flats next to it would lower it to an Ab.

Thanks for all the help. I'm a total beginner when it comes to reading. Normally I learn by ear from recordings, but this time all I have is some sheet music. It's a grind.

[brem]

I've never seen mix sharps and flats in the same sheet.

[rarisgod]

I believe it has to do with declaring an interval and with the key signature as well. Not exactly sure how to explain it, but I know when we were doing an interval test in school (the teacher played 2 notes on the piano, telling us the first note, and then we had to identify the interval and write it out) this occurred once, as sort of a test question.

I believe the notes went from Ab to A, or something like that, but it was a minor second. We couldn't just write a natural sign, because it had to be a minor SECOND, and we had to make it look like a minor second by going up to the next line on the sheet paper...so we had to write Bbb. I THINK that's how it went, it's been awhile. Personally I don't completely understand it, as writing Ab to A would still be a minor second to me.

[Mushroo]

Originally Posted by brem

I've never seen mix sharps and flats in the same sheet.

Really? What about tunes minor keys?

G A Bb A G F# G

for example.

M

[Mushroo]

Originally Posted by rarisgod

I believe it has to do with declaring an interval and with the key signature as well. Not exactly sure how to explain it, but I know when we were doing an interval test in school (the teacher played 2 notes on the piano, telling us the first note, and then we had to identify the interval and write it out) this occurred once, as sort of a test question.

I believe the notes went from Ab to A, or something like that, but it was a minor second. We couldn't just write a natural sign, because it had to be a minor SECOND, and we had to make it look like a minor second by going up to the next line on the sheet paper...so we had to write Bbb. I THINK that's how it went, it's been awhile. Personally I don't completely understand it, as writing Ab to A would still be a minor second to me.

The rule is, if it's a 7-note diatonic scale, each letter name should appear once. So you wouldn't have both Ab and A, or Gb and G#, or Bb and B in the same scale.

The exceptions are scales that aren't diatonic scales, such as diminished or chromatic scales. Those can have more than one instance of the same letter name.

[alexei]

Originally Posted by zac2944

Hmm. Well there's one of my problems. I thought that since the B is Bb due to the key signature, then putting two flats next to it would lower it to an Ab.

Thanks for all the help. I'm a total beginner when it comes to reading. Normally I learn by ear from recordings, but this time all I have is some sheet music. It's a grind.

II would think the same as you did, since key sig. tell you B is flatted by default.
So if the sheet shows a Bb would mean a flatted <B flat> (or A natural). So....

if a flatted <B flat> is A...
what's a double flatted <B flat> ? my logic says it's Ab.

I'm also starting with notation so I assume there's some chapter we didn't read yet.

[Mushroo]

Originally Posted by alexei

II would think the same as you did, since key sig. tell you B is flatted by default.
So if the sheet shows a Bb would mean a flatted <B flat> (or A natural). So....

if a flatted <B flat> is A...
what's a double flatted <B flat> ? my logic says it's Ab.

I'm also starting with notation so I assume there's some chapter we didn't read yet.

B double sharp = C#
B sharp = C
B natural = B
B flat = Bb
B double flat = A

This is true regardless of which key you're in. If you're in the key of Gb (which has a Bb in the key signature), Bb is still Bb and Bbb is still A--it doesn't become Ab!

You are assuming it's relative to the key signature, but it's not.

[Mushroo]

There are 2 main contexts where you'll see the double flat used a lot:

1. To notate a minor interval in a flat key signature. For example, if you're playing a Gb blues, you'll use the minor 3rd a lot for your blues licks. It would be incorrect to call this note A, since it is a minor 3rd, not an augmented 2nd, so it's notated Bbb. (Note: if it's followed later in the measure by the major 3rd--Bb--you'd typically write a natural sign plus a flat before the Bb so it's clear that the double flat is being cancelled out.)

2. Diminished 7th chords. Cdim7=C, Eb, Gb, Bbb (though you sometimes see C, Eb, Gb, A for convenience).

[zac2944]

Originally Posted by Mushroo

B double sharp = C#
B sharp = C
B natural = B
B flat = Bb
B double flat = A

This is true regardless of which key you're in. If you're in the key of Gb (which has a Bb in the key signature), Bb is still Bb and Bbb is still A--it doesn't become Ab!

You are assuming it's relative to the key signature, but it's not.

Thank you. That makes things a LOT clearer.

[zac2944]

Originally Posted by Mushroo

There are 2 main contexts where you'll see the double flat used a lot:

1. To notate a minor interval in a flat key signature. For example, if you're playing a Gb blues, you'll use the minor 3rd a lot for your blues licks. It would be incorrect to call this note A, since it is a minor 3rd, not an augmented 2nd, so it's notated Bbb. (Note: if it's followed later in the measure by the major 3rd--Bb--you'd typically write a natural sign plus a flat before the Bb so it's clear that the double flat is being cancelled out.)

2. Diminished 7th chords. Cdim7=C, Eb, Gb, Bbb (though you sometimes see C, Eb, Gb, A for convenience).

That makes sense. Thanks.

[DocBop]

In general music should be written so it is easy to sightread. Now sometimes a double accidental is easier to read than using an enharmonic. Now in examples and textbooks the double accidentals are used so things layout properly illustration. For example so when writing a scale you don't want a letter name to repeat so you use double accidentals as necessary.

[onlyclave]

PS. It also looks cool.

[HaVIC5]

There are a bunch of reasons academia has deigned to use the double flat/sharp, most of it having to do with intervallic recognition. Every note to the other notes has a predefined intervallic quality, for example, E to G is always going to be some sort of third, and D to A is always going to be some sort of fifth. So when you have E to G#, that's a major third, or E to Gb, that's a diminished third, or double flat third. When you have D to A you have a perfect fifth, but when its Db to A#, it's a doubly augmented fifth, or double sharp five.

This in the real world doesn't have too many immediate applications, since it often is harder to READ the double accidentals, and they are often simplified for the purpose of performance. There are plenty of exceptions, however. Notating the leading tone in minor keyed music can very often be a double sharp. Psychologically, it works a lot better to see a note sharped again when its a common example of an altered melodic pitch, and in general it's easier to read.



The other instance is whenever a double flat will decrease the number of accidentals used. The general rule of thumb when writing accidentals (besides sharps going up and flats going down) is write it so you have the least number of accidentals possible for a given passage. Which would be easier to read?

[MonetBass]

Originally Posted by slybass3000

There is a rule you can apply: use sharps or natural in this case as accendentals when the the line goes up and use the flats for any accidentals when the line goes down. Be concious about the key signature.

hope this help,

Sylvain

A better way perhaps to state that would be:
1) Raise the note for ascending lines (# or natural depending on the key signature)
2) Lower the note for descending lines (b or natural depending on the key signature)

[brem]

Originally Posted by Mushroo

Really? What about tunes minor keys?

G A Bb A G F# G

for example.

M

You mean: G A Bb C D Eb F# G (Gm, Bb relative major)

I guess you're right if you use the rule that no two notes should use the same letter in a diatonic scale.

However, what I was under the impression of is that when your key signature has flats, you keep using flats for accidentals... and vice-versa for sharps.

[Mushroo]

Originally Posted by brem

However, what I was under the impression of is that when your key signature has flats, you keep using flats for accidentals... and vice-versa for sharps.

No, you use whichever is correct for the note's function. For example, in the key of G Minor, you would use F# instead of Gb because the note is the natural 7th, not the flat root.