Why did Segovia use a different pattern for the B minor scale?

Question

I am learning Segovia scales.

Many of the scales have the same pattern - for example, A major and A♭ major scales are the same, up to a shift of 1 fret on all notes. It would make sense to minimize the number of different patterns; in fact, there are only 4 such patterns for major scales (I have convinced myself that we cannot use fewer patterns).

However, for minor scales, there is another idea: B minor and B♭ minor are not derived from e.g. A minor by shifting the pattern up. Instead of that, they have different fingering for all but the highest notes of the scale, and they don't use string 6.

I see two disadvantages of this:

1. One more pattern for the student to learn
2. More position changes when playing this B minor (when compared with e.g. A minor)

What is the reason for this choice? What advantages does it have?

---

The fingerings for all the scales are described e.g. here.

Below are A minor and B minor scales, taken from there:

            A minor

e|------------------------------------------------------------10--12--14--16-|
B|---------------------------------------------9--10--12--13-----------------|
G|--------------------------------------9--11--------------------------------|
D|---------------------------9--10--12---------------------------------------|
A|----------5--7--9--11--12--------------------------------------------------|
E|-5--7--8-------------------------------------------------------------------|

   1  3  4  1  3  1  3   4   1  2   4   1  3   1  1   3   4   1   3   1   3 


e|-17--15--13--12--10--------------------------------------------------------|
B|---------------------13--12--10--------------------------------------------|
G|---------------------------------12--10--9--7------------------------------|
D|-----------------------------------------------10--9--7--------------------|
A|---------------------------------------------------------10--8--7----------|
E|-------------------------------------------------------------------10--8---|

   4   2   4   3   1   4   3   1   3   1   3  1  4   3  1  4   2  1  4   4 


e|---------------------------------------------------------------------------|
B|---------------------------------------------------------------------------|
G|---------------------------------------------------------------------------|
D|---------------------------------------------------------------------------|
A|---------------------------------------------------------------------------|
E|-7--5----------------------------------------------------------------------|

   3  1

            B minor

e|-----------------------------------------------------------12--14--16--18--|
B|----------------------------------------9--11--12--14--15------------------|
G|---------------------------------9--11-------------------------------------|
D|----------2--4--6--8--9--11--12--------------------------------------------|
A|-2--4--5-------------------------------------------------------------------|
E|---------------------------------------------------------------------------|

   1  3  4  1  3  1  3  1  3   4   1  3   1  3   1   3   4   1   3   1   3


e|-19--17--15--14--12--------------------------------------------------------|
B|---------------------15--14--12--10--8--7--5--3--2-------------------------|
G|----------------------------------------------------4--2-------------------|
D|----------------------------------------------------------5--4--2----------|
A|-------------------------------------------------------------------5--4--2-|
E|---------------------------------------------------------------------------|

   4   2   4   3   1   4   3   1   4   2  1  4  2  1  3  1  4  3  1  4  3  1

Answer 1

For all scales on guitar, the best way to approach which to use (whether it be whole scale or a partial scale) is to think where you need to go next.

There are tonal considerations - on open string has a very different tone to one fretted at the 9th fret, for example - but of more importance is where you want your hand to be.

It is not generally considered a good idea to reduce the number of scale patterns you know, but instead be able to play any scale or any mode at any position on the neck in order to use the versatility of the instrument to its fullest.

Answer 2

First off, I would suggest that learning more patterns is actually better, since it allows you to take the same intervals and place them on different strings and increased changes of position gets you more used to having to do that quickly/efficiently, which ends up happening in music. I would also mention that guitar is pretty easy on you as far as learning the scales. When learning piano, there are several fingerings to learn for each type of scale, as opposed to being able to shift it up a fret. You would find similar situations of different fingering patterns on lots of other instruments, like horns and woodwinds.

My guess is that the reason why this scale is starting on the A string instead of the E string is for the reasons I mentioned above. Starting your pattern in a different place will reinforce position changes and alternate patterns. You could ultimately play the same pattern as the A minor pattern by sliding it up 2 frets. I would recommend practicing it both ways and trying to find the similarities between them. The might allow you to have a better grasp of the scales conceptually, while getting you in touch with alternative fingers/position changes, so that when you are trying to figure out the best way to play something in the future, you will have more options readily available to you.