Could anyone tell me/us something about how to use them? 
With progressions examples    (in the key of C)
Last edited by opiekundps2015 at Apr 8, 2017,
Only the first two are functional chords, maj7#11 and bII6, respectively

The "Chopin chord" can only be found on one website and is an exercise in non-chord tones, and the "mystic chord", I'd analyze it similarly unless there's something to suggest otherwise

As with any information, I'd check to see if it comes from a reliable source first. How good are you at identifying functional harmony?

Edit: listened to more context for the "mystic chord". It's not functional tertian harmony.
Where do people come up with these seriously.

Fun fact, the "mystic chord" was apparently utilized by Alexander Scriabin. I happened to see a performance of his composition, "Reverie", a couple of days ago, the local philharmonic played it as a warm-up of sorts before they performed Shosti's Leningrad symphony. But I liked the Scriabin piece as well  
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As this appears to be an exercise in wanting to use "cool" chords without actually knowing what they are, I have the appropriate answers for you:

Lydian Chord - this is a straight up major chord, but if you argue long enough on this forum, everyone will accept that it's now called a "Lydian chord", simply to end the conversation.

Neapolitan Chord - this is a combination of the vanilla, strawberry and chocolate chords. Make sure that each flavour is kept separate though.

Chopin Chord - this is any chord with palm muting. Eg. Metallica use the Chopin chord a lot in their rhythm playing.

Prometheus Chord - this was the long awaited follow up to the Alien chord. When you start playing the chord people are super hyped, but start laughing when the penis snake appears. From there it's downhill.

Mystic Chord - before asking, do you have a hooded robe and how long is your beard.
And no, Guitar Hero will not help. Even on expert. Really.
Last edited by AlanHB at Apr 9, 2017,
Lydian chord is idk that sounds like some jazz bullshit right there. Neapolitan chord functions as a predominant chord (it's a chromatic alteration of the IV chord, even though it looks like a bII I promise I'm right, chords aren't only considered vertically you guitar playing butt monkeys) and in regular use resolves onto the dominant chord. The Chopin chord is nothing, probably just some fluffy piano playing and bad composition. The mystic chord isn't functional it's just a bunch of notes that some Russian loser thought sounded way cooler than they actually do.
Lydian chord - I can only assume you're referring to the chord that Rick Beato has explained a few times, the formula being: 1, #4, 5 (in C: C, F#, G). He's literally the only person I've ever heard mention this chord, and it's honestly a stupid name that no one uses. Just call it sus#4, that's all it is, if you go around saying "play me G lydian" to musicians, they'll just play the G lydian scale, and if you then say "No, the chord" they'll look at you like you're an idiot. Save yourself the embarrassment. 

Neapolitan chord - There are multiple different versions of the Neapolitan chord (named after different European countries, Italian, French and German if my memory serves me well), but the main idea is that it's a major chord built on the b2 degree of the scale (in the key of C it'd be Dbmaj). It's a pre-dominant functioning chord, and is almost always found in 1st inversion (since it's often subbed for the IV chord), which resolves to the V. Doesn't mean you can't use it in root position, in fact when you do it acts as a nice plagal cadence, giving you the sound of a IV - I plagal cadence along with the added chromatic bass line going from the b2 to the 1. Gets more complicated when you start adding in the extensions that are often used with them.

Chopin chord - I could only find one site that explained this chord, and it seems it's just a dominant 7th chord with a b13 (C E G Bb Ab). I can only guess it has some connection to the diminished 6th scale, which is essentially the same as the bebop scale (major scale with an added chromatic note between the 5th and 6th degrees), but whereas the bebop scale just treats that #5/b6 as a blue note, the diminished 6th scale uses the b6 as part of it's harmonic makeup. It's weird and complicated, so unless you're a huge Barry Harris fan and actually use that scale a lot, I wouldn't bother thinking about this chord; it's realistically just a 7b13 chord.

Mystic/Prometheus chord - A chord that's famous for the composition it was used in (called Prometheus, oddly enough), and how alien it sounds. It's this weird jumble of notes that no one really understands how it's meant to be used, because in the piece it's in, it's used in so many different ways, and none of them can be easily analysed. The simplest answer it's a scale played as a chord, that scale being called, you guessed it, the Prometheus scale, also named after the composition (in C: C D E F# A Bb). The scale is essentially just a Lydian Dominant scale without the 5th (super weird sounding), but from there on trying to understand this chord is just a dog chasing it's own tail; it's used so ambiguously that it's famous for being weird. Don't even bother trying to understand this chord, just accept it as some weird thing one composer came up with for his music and move on. Trying to understand this chord functionally is like trying to understand 12 tone serialism functionally.

Lydian is just a sus#4, Neapolitan is just major chord built on the b2, and just forget about the other 2 chords.
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I'd interpret the term "lydian chord" as meaning a maj7#11 chord.  Seems straightforward to me, as a chord symbol which indicates lydian mode.  It could also have a 9th or 13th, but would be 1-3-5-7-#11 as standard.  In modal jazz they might voice it differently, and might omit the 5th.

The others have various roles in classical music, the neapolitan chord being the most common of the three (by far).  Jimjambanx's explanation is not quite right - he's talking about augmented 6th chords (which come in Italian, German and French varieties).  He's right that a neapolitan chord in C major would be a Db in 1st inversion, i.e. with an F bass (Db/F) - but it resolves to G, not to C. https://en.wikipedia.org/wiki/Neapolitan_chord.  

Jazz has similar practices, but calls them "tritone subs", and uses them more freely.  So, in classical theory, a Db7 could resolve to C, but it would be in the key of F.  And it would be a type of augmented 6th chord (not a neapolitan chord) called a "German 6th", spelled Db-F-Ab-B (Db-B being the defining "augmented 6th" interval). https://en.wikipedia.org/wiki/Augmented_sixth_chord 
In jazz, they'd call it a "tritone sub" (standing for G7), and it could resolve to a C chord in any key.

The last two are rarer and more complex.  Chopin was a Romantic, meaning he was was extending functional principles to their limit (based on a thorough understanding of those principles in the first place of course).  
The "mystic chord" is post-Romantic, a sonority invented when that whole system had essentially broken down.  Jazz musicians would see it as resembling a "lydian dominant" chord in a quartal voicing (1-#4-b7-3-6-9), but Scriabin used it less as a chord (the way we might use a chord), more as a source of material.
(OK, you wanna try it on guitar?  See if you can wrap your fingers around this 8-9-8-9-10-10.)
Lydian dominant chords are extremely common in jazz, as dom7 type chords not acting as V chords.  So they'd call that chord C13#11 and use it (probably not in its entirety) to resolve to Bmaj7, B6, Bm(6) or Dmaj7.  You could see it as F#7#5#9/C.

But in short, I agree with the others.  If you're interested in these chords because they have cool names, that's OK - it's good to be curious - but you won't really appreciate their usage unless you're already familiar with the common practices of classical harmony.  They're built on the heritage of tonality and functional harmony - chromaticisms invented at a certain time to make more common changes more interesting.   If you don't understand some of the jargon in the above explanations, you won't be able to use these chords properly, and you'd be better off studying classical harmony from the beginning.  (And if you're not interested in classical music - forget them entirely!)  
If you're interested in jazz, again, only the first chord is common parlance - the other three have zero place in jazz.  (The mystic chord resembles a lydian dominant, but its use is quite different.)

Fun factoid: the Simpsons Theme is in C lydian dominant, and could be seen as an arpeggiation of the mystic chord! (although it adds the 5th as well, and leaves the 7th to the very end).  It resolves in jazz fashion to B at the end.
Last edited by jonriley64 at Apr 20, 2017,
To cut down on false information given after the original burst of posts, this topic is closed.