Most songs in major use the major scale, but I keep seeing guitarists play the pentatonic scale in many vids. It's just a subset of the major scale. So why is it so important and what is it used for?

  • It's quite vague. And far more guitarists will use min rather than maj pent. Not my dv, although I did consider.
    – Tim
    Sep 1 '19 at 16:23

The pentatonic scale(s) leave out two important notes. The major pentatonic uses, in key C, C, D, E, G and A. Missing notes are F and B. They themselves are a tritone apart. The tritone itsellf is deemed to be a dissonant interval. The other 5 blend better with each other - let's face it, 3 of them constitute the major triad in that key! So in any order, those 5 notes will sound cohesive.

The same applies to the minor pentatonic scale notes. In key Am this time. Funnily enough they're the exact same notes as those mentioned in key C. So the same idea applies.

You really need to include tag 'guitar' in the question - as that's partly what you ask. And one main reason why guitarists love to use it is that the way standard guitars are tuned, the notes across two octaves (and a 3rd) are found in a very simple pattern across the strings, within 3 frets of each other. Both maj. pent and min. pent. They just happen to be the same pattern for any major and its relative minor.

It was established a long time ago that the min. pent. notes happen to sound quite effective over major or seventh chords - as found in blues and jazz. So guitarists latched on to it all, and it's probably the one thing that most guitarists like doing - widdling on min. pents.

Better players will use the notes from min. and maj. pents. More knowledgable ones will then have added use in some circumstances of the ♭5 in min. pent. (or ♭3 in maj. pent.) to produce notes from the two blues scales.

And stating that it's just a subset of the major scale, as you can now appreciate, is only half the story!

  • I see so mainly a jazz and blues thing.
    – user34288
    Aug 31 '19 at 16:35
  • @foreyez - no, I haven't said that. There are quite a few well-known songs around that use the major pentatonic, that have nothing to do with that. Amazing Grace or Chopsticks as blues or jazz?
    – Tim
    Aug 31 '19 at 16:54
  • Sometimes guitarists seem to use the pentatonic scale, because they can't follow what's happening in the harmony and they're afraid of trying the dangerous notes outside pentatonics. It's a bluesy choice, but it's also a safe choice! A similar phenomenon is with top20 pop tunes, where chords and melody are done by different people, and quite often the lead melody uses only or mostly a pentatonic scale. Design-by-committee music. Safe choices. Not necessarily because of what it sounds like, but because of lack of skill and/or deliberately wanting to avoid sounding bad or different. Aug 31 '19 at 16:54
  • weird that the 4th (F in key of C) was taken away. I thought the subdominant was as important as the dominant.
    – user34288
    Aug 31 '19 at 18:42
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    @foreyez - that doesn't make sense - to me. It might well be used by better players on the IV bars, but it's a copout for lesser players. And I thought this was guitar orientated, not piano...
    – Tim
    Aug 31 '19 at 18:58