Why do pentatonic scales end up in a note after the root?
 

I am watching these youtube videos where they talk about shapes of pentatonic scales.
For example, Am pentatonic scale as below:

Position 1 starts with A but ends up in C.

http://communicasound.com/wp-content...-1024x724.jpeg

Bm also starts with B but ends with D in position 1.

http://www.guitar-chords.org.uk/scal...cpositions.gif

Don't the scale have to start and end at the same root note?
All the videos start from the root on low E but end up on one note higher on the high E.

Yes. Those patterns are just giving all the choices that are available within reach. They don't mean that an Am pentatonic starts on an A and ends on a C. Those patterns can be linked together so you can play all over the fretboard, so knowing all the possibilities can be helpful.

Those positions illustrate all of the notes in that scale in that position. The pentatonic scale is 5 of those notes at a time by definition. I am no expert at all but finally starting to learn that although it is good to know the shapes because it provides the visual backdrop but it is far more important to know the roots and intervals.

So to answer you more specifically, to literally play the pentatonic scale you would start on the root and play 5 notes which would leave you one interval away from the root.

The pattern and the scale are different things.

The notes in the scale here are a c d e g a. Within the patterns, these notes are repeated, and since the patterns have a different number of notes than the scale, the patterns do not begin and end on the same note. Make sense?

Yep. All it’s telling you is how many notes of that scale are available in the “box”. What’s important is to recognize the where the root notes are.

It's weird that a lot of YT teachers teach position 1 with the shape and play from 5th fret on low E and end on 7th fret of high E.
Then they move to next shape and do the same.
That's confusing.

Do you mean end of the 8th fret of the the high E?

If that's the case, it may be because so many on youtube are not really, "teachers." I wouldn't teach it like that, but my guess is that they're just showing you the pattern, or box, as 1neeto said. If I taught it that way, I would just want the student to understand the difference between the pattern and a scale because the pattern includes more than 1 scale.

I'm pretty much a hack and I understand where you are coming from but I think it is necessary to teach the positions first and then teach how to move from one to the other. The important part though, and I didn't get it at first either, is to understand where the root is and the intervals. But I don't know that it is possible to really comprehend all of that at the beginning. I'm just now starting to make some sense of it. I can't apply it well yet but I'm understanding.

So the way I see it, especially at the beginning, is learn the shape one at a time but as you learn it, try to find ways to make it musical. Don't ONLY run the shape. Does that make sense? Try three and four note combinations over a backing track or metronome or whatever and make them musical. One thing I'm starting to notice that when in doubt, end on the root. So for example, try a four not lick that starts and ends on the root in side that pattern. If I were to start over this is what I would do. This way I could take the time to learn the shape, the roots and the intervals and what each interval sounds like and use that to make musical licks.

I'm not sure if it's allowed here but there is a youtube guy I like for this stuff. I don't want to step on toes so I wont post his name but let me know if you want it and I'll pass it along. I just find that he has an approach that works well for me. I also think some teaching styles work for some but not others.

Funny. I started trying to play the guitar when the only way to be taught was to learn to read music. I went with if it sounds right keep it and if it doesn't sound right don't do it. The first thing I came up with was a minor pentatonic scale shape that moved up and down the fret board with no four fret stretches. I think I saw someone call it a ladder pattern or something. If you keep at it you eventually lean that the pentatonic scale (actually any scale) has notes all over the fret board in all kinds of patterns.