Suppose a song is "in C" and a guitar and bass are playing the notes of C major.

If the singer sings only thirds above the instruments and we isolate the voice, we hear a melody in E Phyrgian:

C  D  E  F  G  A  B   Instrumentals: C major sound if C is emphasized
E  F  G  A  B  C  D   Voice?: E Phyrgian sound!

I doubt this happens often, because:

  • vocal melodies are often hummable and the hummed melodies rarely sound Phyrgian
  • I'd expect the vocal melody to sound like it's in the same key as the harmony, so the singer probably has to not always sing thirds, but also find a way to emphasize the tonic (at least in general)

Or, if the singer sings the same mod a third above the instruments then most of the notes they sing will clash:

C  D  E  F  G  A  B   Instrumentals: C major sound if C is emphasized
E  F# G# A  B  C# D#  Voice?: E Major sound

So how does choice of set of notes in harmony actually work? I know it's hard to make generalizations, but what are some general ways for the people making music together to do so such that:

  • the different voices (such as guitar and vocals) are in different frequency bands
  • the different voices sound like they are in the same key
  • the different voices have similar modes (probably one won't do minor thirds while the other does major thirds)
  • there are pleasing intervals within each voice (for example, both a guitar and a voice each get perfect fourths and fifths in their respective melodies)

I'm sure there are multiple ways of satsifying at least several of these loose constraints: what are some popular solutions?

  • That’s not how vocal melodies are written. In terms of popular ways of writing melodies above chords, all you have to do is study or learn some songs or pieces on whatever genre you are most interested in and each song will demonstrate how melodies interact with harmonies. Commented Jun 25, 2023 at 19:11

3 Answers 3


The short answer to your question is: They both use the same notes. If a song is in the key of C, the harmony, instrumental melodic backgrounds and melody will all use notes in the C scale for the most part.

Regarding your example, if a singer sings a C scale from E to E against a C chord it will not sound like E Phrygian but rather like a melody in C that starts and ends on E. Unless you want a dissonant or avant-garde sound you would not sing an E major scale in the key of C, those melody notes would clash against the harmony. Moving up and down a scale is an extremely basic view of what a melody is, a melody is artistic, not mechanical. It combines different rhythms, consecutive notes combined with leaps, changes of direction and other techniques. It does not have to follow the contour of the background and it does tend to emphasize the tonic in general.

My comments are related to diatonic music, or music that does not stray from the notes of the given key. If either a melody or harmony moves outside of the original key then the other will generally do the same to match it. The important thing is that they both do the same thing to maintain a cohesive and consonant sound. For example, if in the key of C is the song goes to a Bb chord, the melody will almost certainly use a Bb note instead of a B natural at that moment.

If you learn about and understand basic harmony you will realize that it is not necessary to think too much about the specific notes different instruments play together. As long as they are playing the same chords or notes that match those chords the end result will generally work pretty well.


This is being asked under false premises. In a song, everyone plays and sings in the same key. It's never that some play in a key, and others play in a mode - not even a mode of that same parent key.

I think you're asking about harmony between , say, a guitar line and a vox line. Thirds is probably the most common, and easiest to perform. Two voices will be the same. Some of those intervals will be m3, some M3. If we take a very simple example, (in key C) one singer sings CDEF, the other, in 3rds, to harmonise, will song EFGA. So, the 1st harmony is M3, 2nd m3, 3rd m3 and 4th M3. There's no problem doing that, for a lot of folk it comes naturally, and will inevitably sound right. Right because all the notes are diatonic - from the same key (C).

You mention P4 and P5. These would often be the next harmony used. Along with the base note, they will often sound hard - so usually get used as well as the 3rds, for what we call 3-part harmony.CG, DA etc sound quite harsh, so where your notion of 'pleasing' comes from, not sure.

Simplest way to understand what I'm trying to get at is to use the white keys on the piano. Two notes with a white key in between are 3rds m/M, and will always sound harmonious together. Notes with 2 or 3 white keys between won't, but play that 3rd as well and it'll come together.


If you take a C major melody, and sing a new melody which is a diatonic third higher, does it sound like E Phrygian? No, really, try it, with a few different melodies. It is very likely that your new melody will also sound like it's in C major. Additionally, if you were to have two people sing both melodies at once (the new one and the one it's based on), it will almost surely sound like it's in C major- we generally interpret a set of notes played together as having one tonality based on all the notes we are hearing. It would not sound like a C major melody played alongside an E Phrygian melody.

Suppose, though, that you did come up with a vocal melody that truly sounded like it was in E Phrygian. If you sang that alongside a convincingly C major accompaniment, the result would probably sound like C major, because the accompaniment generally has more influence over the perceived tonality of the song than the melody does, and the melody is being heard in the context of the C major harmony. You shouldn't be worrying about one instrument sounding like it's in a different mode than the rest.

Quite simply, if the song is in key N, then all instruments (including vocals) will primarily use the notes in key N, with few exceptions.

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