In language-theory and grammar-theory, a language is the output generated by a grammar.
Let's say "the grammar" is the rules and "the language" is the sentences and words that may be produced by those rules.
For example, we can say that this text "The some the although are is about over on under thin then over we the when." is not part of the English language although punctuation is correct and the words belong to English. That expression is not a sentence in the English language because cannot be generated with the grammar rules (ie: Sentence => subject + predicate, Subject => xxxx, Predicate => [complements] + verb + [complements]) etc.
In terms of chord-progression, I know that "what sounds good" will depend on the "culture" you are, the style of music, what epoch/century is your analysis corpus is located and so on. It's not the same Flamenco, than Jazz, than Chinese popular music. Completely agree. Narrow this question down to western classical music.
So... there are chord sequences that would "violate classical rules". Hey, I already know that one can use whatever chord sequence one wants. But there are chord-sequences that are considered "grammatically correct" and others "not correct".
For this question, I don't care if "the rules existed centuries ago" or the rules are discovered now that we analyzed music from centuries ago. For this question, let's assume the rules just exist in classical music theory books.
I would want to know if the "generative rules" of a "formal grammar" able to tell if "the next chord in a sequence" is "part of the language or not" (ie: Belongs to the set able to be generated by the grammar rules) belong to language level 0, 1, 2 or 3 in the Chomsky's categorization and WHY those rules are in that level.
For more concrete references:
References on chord-progression compiled rules
There's this old VST plugin "Harmony Improvisator" that was able to "generate" chord suggestions in function of the current chord. I don't know if the suggestion was also conditioned by the previous chords before the current one.
- Official page here: http://www.synleor.com/improvisator.html
- Video using version 1 of the plugin here:
- Video using version 2 of the plugin here:
My interest in this question is only limited to a set of rules that might have been the one that the authors of "Harmony Improvisator" could have used.
They say in their page:
Composing with the rules of classical harmonic theory
learn functions and rules by heart in order to create classically correct, colorful music
Related questions in this site
There are other questions on this SE site that reference Noam Chomsky's grammar theory:
This one asking about generative music: What are the newest innovations in generative theories of music?
This other one comparing "learning music" with learning your "mother language": Why is music is taught by reading sheet music?
Chomky devoted his life to the theory of any grammar for any language invented or to invent. This encompasses the human-languages like English, French or Catalan, the computer languages like C++ or Java, or many other languages that are made of "sequences of things".
- Formal grammars in general: https://en.wikipedia.org/wiki/Formal_grammar
- Chomkys's work in particular: https://en.wikipedia.org/wiki/Chomsky_hierarchy
How can I tell what Chomsky's hierarchical level is the "classical rules of chord progressions" in?