*Published: 2016-06-16* This is a summary from the [/r/piano](http://www.reddit.com/r/piano) subreddit FAQ. User `onaz` gives a great summary on good chord extensions to use. I have been playing around with Jazz piano for many years but knowing which extension to use for a chord often eludes me. Turns out there are actually systematic categories for each! I will be assuming chords built of the tonic of `C` for each chord below. Because I'm a nooblet. # Major7 chords ```nohighlight C E G B ``` ## Suitable extensions ### 9th ```nohighlight C E G B D ``` This is a safe note to add for many different voicings ### #11 ```nohighlight C E G B F# ``` This comes from the lydian mode. A normal `11th` (or `4th`) would clash with the major seventh sound as it's an avoid note. However, when we raise the usual note a half-step, we get a very rich `#11` sound. ### 13th ```nohighlight C E G B A ``` The `13th` (or `6th`) won't add very much color to a major seven chord because the function it provides is the same as the normal major seventh. We often talk about how major seven chords (like `Cmaj7`) are interchangable with sixth chords (like `C6`) because of their function. ## Upper Structure Triads To get an instant `13(#11)` sound on a major chord, add a triad built from a whole step above the root. - USII - e.g. D major over Cmaj7, resulting in C13♯11 So if we have a `Cmaj7` chord ```nohighlight C E G B ``` We go a whole step above the root of the chord (which is a `C`). Then we take that note (`D`) and build a major triad from there. Now in addition to `C E G B`, we are adding `D F# A` to get a final chord of `C13(#11)`. ```nohighlight C E G B D F# A ``` # Minor 7th chords ```nohighlight C E G Bb ``` ## Suitable extensions ### 9th ```nohighlight C Eb G Bb D ``` Still a safe note to add. ### 11th ```nohighlight C Eb G Bb F ``` This comes from the dorian mode and is a great note to add. ### 13th ```nohighlight C Eb G Bb A ``` A good note to add in minor voicings. ## Upper Structure Triads For minor 7th chords we can use a USii voicing, in this case the Dm. You'll get a Cm13! - USii - e.g. D minor over Cm7, resulting in Cm13 ```nohighlight C Eb G Bb D F A ``` # 7th chords ```nohighlight C E G Bb ``` Dominant chords provide the most opportunity for color. They are often used in transition and contain the most dissonance in a chord progression. ## Suitable extensions ### #5/b5 ```nohighlight C E Gb Bb ``` ```nohighlight C E G# Bb ``` These usually replace the normal fifth. ### 9 ```nohighlight C E G Bb D ``` Adds more color ### #9/b9 ```nohighlight C E G Bb Db ``` ```nohighlight C E G Bb D# ``` Altering the nine can give you a ton of color and disonnace very quickly ### 11 ```nohighlight C E G Bb F ``` This turns the chord into a sus chord. You'll see that written as `C7sus`. This is one of the least dissonant alterations you can make. ### #11 ```nohighlight C E G Bb F# ``` You'll notice that `#11` and b5 are the same note. `#11` is simply another way to think about it. ### 13 ```nohighlight C E G Bb A ``` Adds more colour (and is a standard addition to our four note rootless voicings.) ## Upper Structure Triads The 7th chords are the most flexible here. You can use any of the following triads to alter the chord (from Wikipedia). - USII - e.g. D major over C7, resulting in C13♯11 - US♭V - e.g. G♭ major over C7, resulting in C7♭9♯11 - US♭VI - e.g. A♭ major over C7, resulting in C7♯9♭13 - USVI - e.g. A major over C7, resulting in C13♭9 - USi - e.g. C minor over C7, resulting in C7♯9 - US♭ii - e.g. D♭ minor over C7, resulting in C7♭9 ♭13 - US♭iii - e.g. E♭ minor over C7, resulting in C7♯9♯11 # Additional Notes Usually many of these alterations are used together to create a dissonant sound to the liking of the pianist. Often you'll see printed alterations in dominant chords caused by melody notes. *Most often you will change combinations of the 5th and 9th to get a sound you like.*