12 bar Blues in Bm scale

Question

The first four bars of the Bminor blues are Bm7 / Em7 / Bm7 / Bm7 What does the 7 mean? Does it indicate that the 7th note of the Bminor scale (A) needs to be included in the chord and the same for Em7, does the (D) need to be included in that chord. Does it mean that it's a 4 note chord?

Answer 1

There's a slight confusion with 'minor seventh interval'. Yes, what Aaron states is correct, and with a minor blues, it's B D F♯ and A (the m7 interval), and the same with Em7 - E G B D. The confusion may come when considering a chord such as B7. Which is essentially a major chord, but with that same m7 note added - B D♯ F♯ A. And the major seventh chord itself, consisting of B D♯ F&sharp A♯.

What I'm getting at is that just because the chord has a m7 interval does not necessarily qualify it for the label Bm7. But in your case here, yes, Bm7( and any 7th chord at all) will consist of the basic triad with the addition of a 7th note - of some description. There are others too, but maybe too far to go into for this answer.

And a major point not to be forgotten - that 7th note from the Bm scale could be either A♮ or A♯ - depending on which minor scale one is using!

Answer 2

The 7 in a chord name means to include the major or minor seventh above the chord's root. A 7 by itself means the minor seventh, an M7 or "triangle"7 means the major seventh; thus, a four-note chord.

• Bm7 means "a B minor triad (B - D - F#) plus a minor seventh above the chord's root, B (A). Bm7 = B - D - F# - A.
• Em7 means "an E minor triad (E - G - B) plus a minor seventh above the root, E (D). Em7 = E - G - B - D.

For a complete explanation of reading chord symbols, see Standard format for jazz chord symbols.

The chord's voicing — the choice or pitches and their arrangement — may or may not include all four notes. This can be explored in the many questions on this site related to chord-voicings.

Answer 3

The first four bars of the Bminor blues are Bm7 / Em7 / Bm7 / Bm7 What does the 7 mean?

It means a minor seventh about the bass pitch B.

...Does it indicate that the 7th note of the Bminor scale...

No.

Bm7 is a chord symbol. That symbol makes not reference to a scale.

A fairly common way to refer, by number, to a scale degree, is with the ^ sign. So, something like Bm: ^7 would mean the seventh scale degree in B minor. You could add accidentals to that, ex. Bm: ^♯7 to mean the raised leading tone seventh scale degree in B minor.

Does it indicate that the 7th note of the Bminor scale (A) needs to be included in the chord and the same for Em7, does the (D) need to be included in that chord. Does it mean that it's a 4 note chord?

Yes, but with no need to reference any scale.

• The pitch A will be included, because that is the pitch a minor seventh above B (and the same for the Em7).
• Yes, it is a four note chord, because all seventh chords are made of four pitches, a chord root with a third, fifth, and seventh above that root.

Answer 4

The question has been answered but maybe some practical things can be added.

The only scale needed to construct or read individual chords is the major scale from the root note. For B with its many sharps this is:

Scale Degree:	1	2	3	4	5	6	7	8
Note:	B	C♯	D♯	E	F♯	G♯	A♯	B

For any chord the little m immediately following the root note does not refer to a minor scale but to the fact that the 3rd degree is diminished (made smaller or minor = small in Latin). So the note we play in the chord is not D♯ but D which is a 1/2 step lower.

Then the 7 somewhat confusingly refers to the dominant 7th or 7♭. To explain this ‘dominance’ would take us deeper into harmony and how certain intervals ‘feel’. Note that this seventh can also be called a minor seventh interval from the root note, but again this does not mean it is the 7th note of ‘the’ Bm scale. So Bm7 is made of B D F♯ and A.

The other seventh chord that includes the actual 7th degree A♯ is called the maj7 (major as in big in Latin). It is less common in straight Blues but very common in Jazzy blues.

When we extend the scale over two octaves we get another set of scale degrees with higher numbers such as 9th or 13th and this is needed when getting to more interesting chords in Blues and Jazz, such as B9 which includes the 9th degree, i.e. C♯ which is one step up after the 8th degree. It’s important to remember that chord symbols are not explanations of what is in a chord or how exactly it should be played. They are abbreviations and 9th chords in fact include the 7th degree as well, so these are 5 note chords.

Since playing actual music does not leave any time to figure out which notes should be played when we see a chord symbol, guitarists normally start with standard shapes and learn to move briskly between them. Knowing which notes belong to which chord is then an additional skill which might be useful when finding new ways to play chords (coming up with what are called voicings) but it is perfectly possible to be a great guitarist without even knowing the notes in the major scale - as long as we can match chord symbols with hand positions on the fretboard and make them sound good, or simply ignore any sheet music and play by ear.

The minor 7th chord is a 4 note chord with notes 1, 3♭, 5 and 7♭ but that does not mean we always have to play all those notes, and we can also play some of them on more than one string (since we have 6!). What notes should actually be played when the sheet music says Bm7 depends a lot on what we’re playing and who we are playing with. In my experience | Bm7 | Em7 | Bm7 | Bm7 ] is not the most common way to strum a minor blues because the insistence on the 7th makes it all sound not just sad but as if it is pulling somewhere. I feel it as more annoying than anything else. If I played it I’d keep going back to the plain minor chords and use the 7th more for effect. Another option is to use substitutions on some of the beats in the bar. If a lead guitarist is there as well, they are likely to be using the 7th in their playing so there is no need for the person playing chord accompaniment to include it.

Finally, if we want to think about scales in connection with blues playing then a Bm scale (natural, melodic, harmonic or even Jazz) is not the best place to start. A scale will be useful (but not essential) when we want to improvise over blues changes. A good first step is to learn the minor pentatonic scale and find out how to play it up and down the whole fretboard. Some of the greatest blues lead players stick pretty much to the minor pentatonic, so it’s possible to play many interesting solos with just those five notes (penta-tonic = five tones in contrast to the Bm scales which are all 7 note scales).

Starting with B, the minor pentatonic is:

Scale Degree:	1	2	3	4	5	6
Note:	B	D	E	F♯	A	B
Degree of B scale:	1	3♭	4	5	7♭	8

Notice that these notes make Bm7 chord with an added 4th.

Any note at all can be added to this in solos or chord ornaments as long as most of the notes belong to the scale or the chords so that the extra notes don’t sound like mistakes. There is one extra note which is important to mention. This is the 5♭. In B it is F, and a minor pentatonic with that becomes a six note scale, the ‘blues’ scale. The F is very powerful because it sits between two agreeable intervals, the 4th and 5th, and that makes it disturbing since frequencies which are close but distinctly mismatched tend to upset humans. The B-F interval is called the tritone or devil’s interval, but I don’t think that’s why the blues was sometimes called the devil’s music!

Remarkably enough, the minor pentatonic is great with both minor and major blues chords. There is also a major pentatonic but this sounds more country or even Eastern so it’s not used quite as often.