Bach Chorales in Xfer's Cthulhu? What's behind this?

[vegaron]

I'm trying to understand the theory behind Xfer's Cthulhu Chords Module.
You can chose from a set of chords and there are over a hundred Bach Chorales. Granted, they do sound like what I expect from classical music, but why? I only see random chords there without any system behind them. For example, playing two "equal" notes but in different octaves don't result in same chords. Or rephrasing that as a question: Did Steve Duda have a choice, when he assigned the chords to a specific note?

[JumpingJackFlash]

I'm trying to understand the theory behind Xfer's Cthulhu Chords Module.
You can chose from a set of chords and there are over a hundred Bach Chorales. Granted, they do sound like what I expect from classical music, but why? I only see random chords there without any system behind them. For example, playing two "equal" notes but in different octaves don't result in same chords. Or rephrasing that as a question: Did Steve Duda have a choice, when he assigned the chords to a specific note?

Are you asking about the harmonisation of Bach Chorales (in general), or the way Cthulhu works?
There are countless resources on the former, but I know nothing of the latter.

I would however be curious to see an artificial harmonisation of a chorale melody in the style of Bach. I doubt it would be effective, but I guess technology is improving all the time...

[jancivil]

they do sound like what I expect from classical music, but why?

IF the question is why do things sound like classical music, generally, it's a rather large subject.
I have a vague understanding of the plugin and I tend to doubt the use of it involves care to voice-leading. So here's one reason one might say 'I doubt it's very effective'. JS Bach is all about voice-leading, *part-writing*. So who knows what the connection here will be.

I don't have time to wonder about why the developer made those choices (the application seems bizarre) and my expectation is not high that you'll have much help here for that answer.

[ravasb]

This is from the Xfer forum:
https://www.xferrecords.com/forums/cthu ... h-chorales

How are the 168 'Bach chorales' presets mapped to the BWV classification system?

Steve:
I don't think there is a direct mapping, this or something like this might apply:
http://sporadic.stanford.edu/Chorales/

[jancivil]

4-part Chorales: BWV 250–438

[JumpingJackFlash]

This is from the Xfer forum:
https://www.xferrecords.com/forums/cthu ... h-chorales

How are the 168 'Bach chorales' presets mapped to the BWV classification system?

I can't access that forum without an account (which I CBA to create).

Bach's Chorale harmonisations have been numbered in several different ways in different collections (and there have been several).

In total, over 400 of Bach's 4-part chorale harmonisations still exist. Most formed part of a larger work (such as a Cantata). The BWV numbering starts with his Cantatas; BWV 1.6 is the chorale (Wie schön leuchtet der Morgenstern) that concludes Bach's first listed cantata for example. This particular harmonisation is not listed in the well-known (but poor) Riemenschneider collection, but it can be found as number 378 in the 1898 Richter edition, and number 393 in Terry's, 312 in Erk's (vol 2), and so on.

In many cases, only the chorale has survived and the rest of the work has been lost. These generally have numbers ranging from BWV 253-438 (although some of these may have been stand-alone works, possibly for pedagogical purposes. Also, a few recently discovered chorales have much higher numbers).

If you need to know how to find a particular chorale, let me know and I can provide you with relevant numbers/collections.

[vegaron]

I have a vague understanding of the plugin and I tend to doubt the use of it involves care to voice-leading.

Well, you are right doubting that. Cthulhu only provides huge sets of chords, which however seem to belong to a certain "family" (I don't know a proper name for that). And what I wanted to ask, is how or why these sets of chords belong together. I vaguely know about progressions but my knowledge on progressions does not exeed the use of major and minor chords. Maybe this is what I really wanted to ask without knowing it and maybe my question answers that already... Bach seems to use a lot of "unusual" (sorry) chords like 6th, 7th, 9th and I guess I need to know how to build progressions from chords like these.

Maybe that's it already. I think I should look into these chorales and try to analyse them.
Thank you guys for your responses. I don't know why, but I think you helped me finding my true question.

[Richard deHove]

Judging by the chord order I believe that they are mapped chronologically, that is from left to right in playing sequence. There are no other meaningful relationships to the keys or octaves that I can see. If you import a midi sequence into Cthulhu then that's how it auto-maps so I guess that's what Xfer did: they had a bunch of midi files and just imported them and saved. It'd take a lot of effort to map them in a more meaningful way.

[VariKusBrainZ]

I thought it was because these are the sort of chord changes Deadmau3 limits himself too.
Certainly always reminds me of his style when I play with them.

As mentioned above theyre mapped out linearly time wise

[Michael L]

I also wondered about a possible "rationale" for the chorale chords in Cthulhu
However, there's an app for that-- a $3 mac app (windows soon) called Bach Browser that analyses the Chorales, plays them slow, etc. Well done!
https://harmonia.illiacsoftware.com/pro ... ch-browser

[cturner]

Steve Duda explains his choice of Bach in this video done of him at The Pyramid:

https://m.youtube.com/watch?v=MOUkI5hH2HY

Generally pretty interesting, plus there are two more parts.

HTH

[Michael L]

^^^ Great video, says he "just fed in midi chords" from Chorales because they are 4 notes-- 47:42

[JumpingJackFlash]

Maybe that's it already. I think I should look into these chorales and try to analyse them.

Absolutely! This is great way to learn about harmony and voice-leading etc. You don't need a fancy app for that though, just get the scores and study them. You can get them online from a number of sites (be careful, some contain errors). Google Bach's four-part chorales and you should get a lot of stuff.

Bach seems to use a lot of "unusual" (sorry) chords like 6th, 7th, 9th and I guess I need to know how to build progressions from chords like these.

Actually, Bach's four-part chorales are relatively basic in their harmonic language, that's one of the reasons why they're good to learn from. There are sevenths, but nothing bigger than this (no ninths etc.)

Most of the sevenths are diatonic (with the exception of secondary dominants). By far the most common is the dominant seventh, V7. But you also see the diatonic sevenths on the second, fourth and sixth degrees, as well as the seventh degree of the minor key which is the only diatonic diminished seventh.

In all cases, good part-writing dictates that the seventh note resolves downwards by diatonic step.

V7 usually resolves to the tonic, or less often to the submediant chord.
Diatonic sevenths on the second and fourth degrees generally resolve to the dominant chord.
The diminished seventh in the minor key resolves usually to the tonic, or occasionally dominant chords.

It's hard to explain properly on a forum such as this. As I said, studying actual chorales with the music (and hearing them too) will likely be more fruitful.

[cturner]

+1 @JumpingJackFlash

[vrbunkos]

JumpingJackFlash commented:
"I would however be curious to see an artificial harmonisation of a chorale melody in the style of Bach. I doubt it would be effective, but I guess technology is improving all the time..."

Yes, foe example, composer and A.I. researcher, David Cope has made available for downloading several thousand A.I. composed Bach[like] chorales on his website:

http://artsites.ucsc.edu/faculty/cope/5000.html

I would tend to agree. To me, they sound quite a bit like J S Bach, but are somehow boring over all, like an uninterested student's routine harmony exercises. Still, as an A.I. experiment, they have a certain curiosity value. It's an interesting algorithm he uses, explained in his books on A.I. music.