In what cases do you really need to play the octave rather than just the root, third, and fifth of the chord? I see other people playing chords and in some places (for example: key of C) they just press first and third key, others press 1st, 3rd, and 5th keys, and then others play the chord with the octave above. How do I know which parts of the chord I need to play?

please see picture: https://i.sstatic.net/UJS9r.jpg

  • Welcome to the site! It seems you're asking about octave doubling (play the note 1 octave above the bottom of the chord). You can leave notes off of a chord, implying the harmony, or double certain chord parts, strengthening that note of the chord.
    – Josiah
    Jun 3, 2015 at 17:50
  • This is like asking, "I've seen so many double consonants used, but writing only one is much easier - which one is correct?" Jun 4, 2015 at 6:13
  • Off the top of my head, Chopin's Prelude in C Minor.
    – user28
    Jun 4, 2015 at 13:36

1 Answer 1


This is purely to the discretion of the composer or in some cases the interpreter.

If you follow strictly by classical counterpoint, typically you want some form of a triad (1-3-5) without repeating notes if possible.

There are many cases however where a composer leaves out the 3rd of the chord to leave it hollow. Omitting the 3rd will take away the happy/sad tonality of the chord, so it can sound kind of numb or even mysterious.

Often you would play the octave (8th) just to create a large voicing. A piece I'm working on now, Rachmaninov's Liebensfreud, ends with an enormous chord across 6 octaves. This is sounds really triumphant and is truly wonderful in the context of the song.

I suggest you try out different voicings in different places and figure out what you like best.

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