(@Dominik Gräber, this one does contain a bunch of theory again 
)
Basically, I was taking a shower (yes I do take those) and I was thinking about harmony and more specifically about functional harmony. As an introduction first I'll probably need to explain what cadences are.
Basically cadences indicate how chords relate to each other and they are usually indicated by means of roman numerals so If you would build chords within the major scale (ionian) you would have the following roman numerals:
Where upper case is major and lower case is minor and 0 implies diminished.
Now how these relate is indicated by that of cadences. In principal there are 4 cadences:
First let's define a key (I'm going for the key of D here because I like the key of D). This gives us the following roman numerals:
Where this gets interesting is when you want to put either the ii, iii,vi or vii0 chords before the I chord. Because these can suddenly function as IV, V, iv or v chords and here's why:
If you take the ii-I you have Em-D. However, Em can also be an inversion of a G6 without the fifth where G6-D which is IV-I which is a plagal cadence. So the ii chord can function as a IV chord IF you put it in front of the tonic. If you then take the iii-I you have F#m-D. However, F#m can also be an inversion of an A6 without a fifth where A6-D is V-I which is a perfect cadence. So the iii chord can function as a V chord IF you put it in front of the tonic. If you take vi-I you have Bm-D. However, Bm can also be an inversion of Gmaj7 without the root(yes adventurous I know but it works) where Gmaj7-D is IV-I which is a plagal cadence. so vi can function as IV if you out it in front of the tonic. Lastly, when taking viio-I you get C#dim-D. However, C#dim can also be an inversion of A7 without the root. Making it V-I since it would be A7-D. So the viio can function as as a V chord IF you play it before the tonic.
Another example would be the famous progression Am-G-F-G which really is i-v-iv-v but I think it comes in handy if you guys figure out yourself how that one works if you're really interested in this stuff.
Hope this was useful for somebody
)Basically, I was taking a shower (yes I do take those) and I was thinking about harmony and more specifically about functional harmony. As an introduction first I'll probably need to explain what cadences are.
Basically cadences indicate how chords relate to each other and they are usually indicated by means of roman numerals so If you would build chords within the major scale (ionian) you would have the following roman numerals:
| Degree of scale of the root not of the chord | Roman numeral |
| 1 | I |
| 2 | ii |
| 3 | iii |
| 4 | IV |
| 5 | V |
| 6 | vi |
| 7 | viio |
Where upper case is major and lower case is minor and 0 implies diminished.
Now how these relate is indicated by that of cadences. In principal there are 4 cadences:
- Perfect Cadence ( V-I): This cadence is frequently found at the end of pieces of music because it gives a feeling a closure and is therefore also referred to as the full close. The sense of finality comes from either from the dominant to the tonic or the leading tone rising to the tonic.
- Imperfect cadence(I-V, II-V or IV-V): This is any chord followed by the dominant chord. They sound unfinished and give the impression the music is continuing after. It's also referred to as the half close.
- The plagal cadence(IV-I): this cadence is the subdominant chord followed by the tonic. This also gives a sense of completion.
- The interrupted cadence(V-?): this cadence is the dominant chord followed by any chord that's not the tonic. Basically, it leads to listener to expect the tonic while not getting it. it is also referred to as the half close.
First let's define a key (I'm going for the key of D here because I like the key of D). This gives us the following roman numerals:
| Chord | Roman numeral |
| D | I |
| Em | ii |
| F#m | iii |
| G | IV |
| A | V |
| Bm | vi |
| C#dim | viio |
Where this gets interesting is when you want to put either the ii, iii,vi or vii0 chords before the I chord. Because these can suddenly function as IV, V, iv or v chords and here's why:
If you take the ii-I you have Em-D. However, Em can also be an inversion of a G6 without the fifth where G6-D which is IV-I which is a plagal cadence. So the ii chord can function as a IV chord IF you put it in front of the tonic. If you then take the iii-I you have F#m-D. However, F#m can also be an inversion of an A6 without a fifth where A6-D is V-I which is a perfect cadence. So the iii chord can function as a V chord IF you put it in front of the tonic. If you take vi-I you have Bm-D. However, Bm can also be an inversion of Gmaj7 without the root(yes adventurous I know but it works) where Gmaj7-D is IV-I which is a plagal cadence. so vi can function as IV if you out it in front of the tonic. Lastly, when taking viio-I you get C#dim-D. However, C#dim can also be an inversion of A7 without the root. Making it V-I since it would be A7-D. So the viio can function as as a V chord IF you play it before the tonic.
Another example would be the famous progression Am-G-F-G which really is i-v-iv-v but I think it comes in handy if you guys figure out yourself how that one works if you're really interested in this stuff.
Hope this was useful for somebody
