Confusion about using scales and modes together in a solo?

Question

Ok so my music theory knowledge is limited. I have been playing guitar for a couple of years now, mostly by ear and I often struggle in applying theory.

While writing a solo I wondered whether I could mix up modes and different scales to make it sound interesting. Let's say I want to write a solo for a song in the key of C minor and as it is a metal song it mostly uses power chords, will any minor scale work over it?

Can I use say a C minor pentatonic, C pure minor, C harmonic minor and C phrygian together in the solo (considering the chord progression is mostly power chords)? If not what can be my scale options while staying in a particular key?

Answer 1

When you want to compose a solo that consists of multiple scales, you have to make sure that the transition between the scales will be smooth - the less notes which are different, the easier the transition between the scales will be.

Lets analyze the scales that you've given us:

C Natural Minor: C, D, Eb, F, G, Ab, Bb, C.
C Harmonic Minor: C, D, Eb, F, G, Ab, B, C.
C Phrygian: C, Db, Eb, F, G, Ab, Bb, C.

The reason I did not include the C Minor Pentatonic is that the best usage for it when writing an interesting solo is as a guideline - see which notes you want to stick to the most.

Now, between the C Natural Minor and the C Harmonic Minor there is only one note different, and the same between the C Natural Minor and the C Phrygian. This means that you would want to stick to the C Natural Minor the most, as it will give you the most freedom, never use the notes B-Bb or D-Db together, and be aware that using the chords Bb5, B5, Db5 and D5 will require you to plan ahead and it will make the song more complicated. If you want to make your song really interested, throw in some Ddim5 and Abdim5-es and watch it become a lot darker.

Apart from that, you're free to do whatever you want. Have fun with creating your solo!

Answer 2

In C minor, particularly over power chords, these all sound good - C natural min., C harmonic min., C melodic min., C Dorian, C Phrygian, and C Locrian (to a degree). Of course, C pent.min. and C blues work as well. Without any minor flavor being revealed in the power chords, you could possibly use C major as well. Bb major works, given that it has Bb and Eb, which reflect the C pent.

Also, depending on what roots the other chord have (maybe there's an Eb power chord) other scale notes can come into play. It's probably easier to write the 2 or 3 notes that won't work well! But even they can be made to fit...

A peek at the actual sequence may give us more ideas.

Answer 3

again, some simple rules and observations for working with modes in this case;(1) your song in "C minor" is already in a mode known as C-Aeolian (the natural minor 6th mode of the C-maj. scale)(2)Ionian and Aeolian are the exception to the rule and the only 2 modes of the C-Maj., scale that can have a tonal center/key- depending on how they are used (3)If you're using more than 2 chords in a functional harmonic progression, in or related to C minor then you are not playing in a mode, but in the normal natural minor diatonic setting.(4) switching into or creating a mode is not done buy simply changing the "scale(s)" that you use, but changing the accompanying chords to a modal motif-sequence (aka:Modal Harmony)and applying the appropriate mode(s) to it (5) i.g. you would have to leave the key of C minor and create a modal-sequence motif of not more than 2 chords (general rule) in which the modal-sequence is not related (as in relative) to the key that the piece is in. Of course some of these rules can be broken or bent, depending on the modal type being used.