Do you happen to refer to the chromatic scale? If you do, the chromatic scale is a scale that contains all of the twelve notes that we use in current music theory. If you're a beginner, I wouldn't bother thinking about when to use it since the practical usage of the chromatic scale is a bit unusual subject. It can be used to create straightforward metal riffs though if you're into that.

To play a chromatic scale, you can just play an open string and every fret until the twelfth in a sequence. Then you have played every note you can play on a guitar over one octave. You should familiarize yourself with the chromatic scale since it's good to know the names and the positions of different notes.
12 tone scale does typically refer to the use of all 12 notes found in the chromatic scale. It was widely used in some early 20c classical music popularized most notably by Arnold Schoenberg. However, its use was not so much as an actual scale but as a way of writing music that was atonal - not tied to a specific key.
Yeah, I've never seen all 12 tones being used in any of the stuff I play. At most, you might get a short chromatic progression that uses 3, 4 or 5 notes, which usually involves some chord inversions. As already suggested, knowing the names and positions of the different notes on the neck is far more important.
To use the chromatic scale you don't need to use all of the notes in it. Just like a minor key song doesn't need to use all notes in the minor scale. Some kind of chromaticism is used in a lot of music (for example the intro of Stairway to Heaven uses a descending chromatic bassline: A-G#-G-F#-F). But yeah, it is rare that a song uses all of the 12 notes.
Quote by AlanHB
Just remember that there are no boring scales, just boring players.


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Believe it or not, I can easily give you a good but somewhat long answer. The "Twelve tone scale" is either referring to the Chromatic Scale (all the notes of the octave and there are twelve in western music) or a Twelve-Tone Row (a classical compositional technique where one plays all the chromatic scale's notes but doesn't repeat a single one before the others are played). The latter is best achieved through whole-half or half-whole movements. Both are important parts of serialism (a technique for writing atonal music) and are very symmetrical (like Death the Kid from Soul Eater).

Serialism is fun to mess around with but not too melodic on its own. However learning to play the chromatic scale is useful for fast runs and learning the notes on the neck of the guitar. Sorry for the long answer but I have quite a bit of knowledge on the subject (I researched it for a while in my spare time).
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Quote by jazz_rock_feel
Use it all the time. You only yolo once.

One doesn't just use chromatic scales. They are a way of life.
There's no such thing; there never was. Where I am going you cannot follow me now.
Listen to Slayer guitar solos, you might understand it then :')

On a serious note, if you are referring to the 12 tone row then this is the technique used in serialism (composing music using a series of the 12 notes opposed to writing within a particular key or tonal centre which would mostly only include 7 notes which are ordered in certain distances called intervals to create a particular feeling or mood). Some very interesting music has been created from this 12 tone row. Have a little look on Youtube at '12 tone row' and you will see how it is used. In terms of writing using 12 tone row, its rather difficult to make something sounding interesting to listen to unless its intended to be atonal for the purpose of a movie soundtrack or something. I think the reasons behind using it was to create music without sticking to using predictable chord progressions or melodies/note intervals. To me it feels like to much of an effort to purposely not write within a key. Why not just write something you like and not think about being in key or not being in key?
^ Lul wut? No, just no.
Can someone close this thread already? The question has been answered pretty thoroughly.