How to find the key of a song...Fast !

viz

octatonic said:

thegummy said:

octatonic said:

Sounds like a few people don’t know what a secondary dominant is.

Is that in response to my post?

If so, I don't know what it is but want to.

It wasn't directed at anyone in particular but the notion that you can use the dominant chord to figure out the key of a song is fundamentally flawed.

In a chord progression that is wholly within one key then it works fine- you have a Dm7 G7 C Maj7 progression then you can take the dominant chord and go down a 5th and find your key- in this example it would be C major.

Ok, well how about this then:



How do you know when it modulates key and when the dominant chords are secondary dominants, which is a chord that is dominant to a chord other than the tonic?

Using a dominant as a way to work out the tonic has very limited use.

octatonic said:

Sounds like a few people don’t know what a secondary dominant is.

Also any song in dorian, lydian, mixolydian etc has their two major triads in a different position relative to the tonic than a major song does. 

For example, Lydian songs such as Flying in a Blue Dream have their major triads as the I and the II. 

carlos

octatonic said:

How do you know when it modulates key and when the dominant chords are secondary dominants, which is a chord that is dominant to a chord other than the tonic?

Using a dominant as a way to work out the tonic has very limited use.

Isn't it curious that at some point this was pop music? I agree with you, @octatonic but if you're dep'ing in a covers band down the local watering hole, then you need to be able to do a passable solo without too much to go on. I don't like this IV/V as major triads way. I prefer to find a few triads that work (just major/minor) and then build on them. Every clam is a passing tone and the right note is always a semitone away.

bigjon

octatonic said:
the notion that you can use the dominant chord to figure out the key of a song is fundamentally flawed.

In a chord progression that is wholly within one key then it works fine- you have a Dm7 G7 C Maj7 progression then you can take the dominant chord and go down a 5th and find your key- in this example it would be C major.

Ok, well how about this then:



How do you know when it modulates key and when the dominant chords are secondary dominants, which is a chord that is dominant to a chord other than the tonic?

Using a dominant as a way to work out the tonic has very limited use.

Ironically I use exactly this approach when soloing over jazz standards like All The Things You Are - I use the dominant chords as a way of deciding what key I'm in AT THAT PARTICULAR MOMENT. In other words I don't think in 'secondary' dominants at all. So if I've got a VI7 ii V7 I progression like A7 Dm G7 C I treat the G7 as the dominant of C (it's the only dominant 7th chord in the scale of C major harmonised in 7ths) and I treat the A7 chord as the dominant of Dminor (it's the only dominant 7th chord in the scale of D harmonic minor harmonised in 7ths). 

Want to know what the key of the whole song is, if it's a jazz standard? Find the last dominant 7th chord before the end of the tune and treat that as the dominant / V chord of the song. Works for All The Things You Are and the vast majority of jazz standards.

octatonic

Addressing viz/carlos/jon above ^^^

My point is that it shouldn't be taken as gospel- it is just one technique to use.
I also use the V7 to get the I in a lot of music but the less experienced amongst us need to know that exceptions exist and eventually that approach will run out of theoretical road.

viz

octatonic said:

Addressing viz/carlos/jon above ^^^

My point is that it shouldn't be taken as gospel- it is just one technique to use.
I also use the V7 to get the I in a lot of music but the less experienced amongst us need to know that exceptions exist and eventually that approach will run out of theoretical road.

100% agree with you @octatonic - I mean like both you and @bigjon are saying, any perfect cadence, whether it be a V-I (or V-i) or a VI-ii or anything else, is going to be a resolution, even if momentarily. But as you point out, you can’t rely on it to find the piece’s key reliably as more complex pieces have cadences and modulations all over the place.

You simply have to listen to the whole thing and listen for home. It’s a very difficult thing to describe because to musicians it’s obvious most of the time, and where it’s genuinely ambiguous (et Sweet Home Alabama), rules aren’t going to help because it’s in the interpretation. Many of these circular or repeating progressions can be forced into one or another key just by how / where you put the turnarounds for example. 

I think the best way of teaching this is to start with simple songs and pieces and let people get familiar with hearing the home key, then building it up. The ability grows with experience. I don’t think methods such as using neighbouring major chords to help identify the home are useful, because as I say, that only works for major pieces with no secondary dominants or other borrowed chords and it’s a convoluted way of identifying home anyway!