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* [[Music Theory - Diatonic Chord Progressions]]
* [[Circle of Fifths]]
== Notation ==
In terms of traditional musical notation or guitar-specific tablature, modulations aren't specifically notated. The non-diatonic notes for a certain key simply appear. For traditional notation, the key signature may change; however, this is typically reserved for the start of new section. Rather, you'd see more {{s}}, {{b}}, and {{natural}} signs appear next to notes. For guitar tab, there is no key signature - you would simply see notes used that were not used before that point in the song. Knowing that there is a key modulation is not necessary for the performance of particular piece; it is only necessary for understanding it in terms of theory.
In terms of harmonic analysis, modulations alter the roman numerals used to mark chords. For example, while C is the I chord of C Major, it is the III chord of A Minor. The key must be specified for this analysis to make sense, and sometimes there is overlap. For instance you may see:
'''Chords -''' C F G C Em Am D G
'''Analysis 1 -''' C: I IV V I iii vi
'''Analysis 2 -''' G: vi ii V I
You can see the "C:" and "G:" in the respective analysis lines indicating the key, with the following roman numerals outlining the member chord from that key. In this case there is overlap, where we may interpret the Em and Am chords as belonging to either key. In other cases where the point of modulation is unambiguous, you may see this condensed to a single line:
'''Chords -''' C F D G
'''Analysis -''' C: I IV G: V I
When discussing modulations outside of a piece of music, we can use an arrow, such as "=>" or "->" to mark the modulation. For example, "C -> Am" or "C => G". If we want to make such modulations generic to any key by using roman numerals, this can get a bit more tricky. For example, if we want to discuss a modulation from a major key to a minor key whose tonic note is the 6th note of the major key, we could say "I -> vi". The uppercase "I" and lowercase "vi" indicate that the original key is major, but the new key is minor, and the "vi" also indicates the new key's tonic note is the 6th's note of the original major key. But what if the tonic note of the new key is non-diatonic to the original key? Then we have to use a {{b}} or {{s}} to indicate that. So moving from C -> A{{b}}m could be generically written as "I -> {{b}}vi". Cm -> A would be written "i -> {{s}}VI" - the 6th note of C Minor is A{{b}}, but we sharp it to get A.
== Common Modulations ==