Are the primary chords of the major scale (I IV V) enough to make any major scale melody sound good? These chords together seem to encompass all 7 notes of the key.

I ask this because as I'm learning songs I know in different keys I'd rather just focus on these three chords for now. I'm just playing by ear, and so far I find this to be true. But I want to check with other musicians.

I'm talking about the major scale as I found minor to be a bit different.

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    If you're learning all those songs in new keys, it's pretty counter-productive to only use I, IV and V. The point being, you'll eventually have to re-learn them to get them right. Either only play songs with those three chords, or go a bit further and put in the other three chords, which is probably what they'll have extra. Bear in mind that, put simply, the other three chords are the relative minors of I, IV and V in the same key. C/Am, F/Dm and G/Em.in key C. – Tim Apr 7 at 11:12
  • Any note can sound good above any chord. – bjb568 Apr 8 at 0:19
  • Just moving from 3 to 4 chords in your base alone will massively increase the amount of pieces you can play, which makes me wonder whether you're solving the wrong problem. – Mast Apr 8 at 11:11
up vote 17 down vote accepted

A melody diatonic to the key can be accompanied with just I, IV and V chords, but this will give a less rich harmonization than using a wider variety of chords. But based on your question, you want to keep things simple.

That being said, do not feel you must match one of these chords to every single note of the melody. Using a reasonable harmonic rhythm, some of the melody notes, even though they belong to the key, will create a dissonance with the harmonizing chord. Listen carefully so you can harmonize in such a way to resolve these dissonances and make them pleasing.

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    “this will give a less rich harmonization than using a wider variety of chords” – “rich” being obviously subjective and relative. For some melodies, are just right and all what's needed, especially if the melody is sometimes dissonant to the harmony and thus already creates extra colour. – leftaroundabout Apr 8 at 9:40
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    More rich does not equal better, of course. It depends on the piece. But a dessert with more sugar and fat is objectively more rich than a dessert with less, no matter whether or not it tastes good. Musical taste is what is going to decide the right amount of "richness". – Heather S. Apr 8 at 11:02
  • totally agree on dissonant notes. In the beginning, some melody steps can be left un-accompanied. Sometimes it's easier to just play the chords when the melody reaches the right "resting" points. – Mordechai Apr 8 at 18:11

Short answer. The short answer is yes: because all 7 scale degrees are represented by one of the chords, it is possible to make a harmonisation that only uses I, IV, and V. This is pretty close to how a typical treatise of music theory starts: start with these harmonies, and add more as need be.

Long answer. The longer answer is no. Although you can string together a progression of I's, IV's, and V's to accompany any melody, this does not necessarily mean that the accompaniment sounds good. This has to do with structural functions that each of the harmonies imply.

Concretely, a typical musical phrase will develop (on the large scale) as I IV V I or a variant thereof (e.g. I ii V I or simply I V I). There might be some other chords in between, but most likely all earlier incarnations of IV and V are in some inversion or otherwise have a weaker structural function. If you arrive on a V, in a lot of situations the only way out is to go to a I afterwards. Similarly, the strongest tendency for IV is to go to V (although back to I is also ok).

This is where other chords start coming in handy: if you move to IV or V too early, your melody is over and has to resolve. But sometimes you want to stretch it a bit longer, and then chords like vii˚, vi, iii, ii, and inversions of all triads become more important.

So what now? The harmonies I, IV, and V are certainly enough to get you started. But as you practise, you will start to notice that you want to do more, and that is probably the right time to add other harmonies to your repertoire.

  • note that the songs I play are mainly children's songs, christmas songs, traditional songs, pop songs. Think silent night, london bridge, amazing grace, my heart will go on, somewhere over the rainbow. stuff like that. – foreyez Apr 7 at 1:40
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    @foreyez: so maybe my terminology feels like overkill. However, these songs have the same overarching harmonic frameworks as major works of classical music! But you might be right that the 'simpler' the song, the more likely that I, IV, and V suffice. – Remy Apr 7 at 2:44
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    @foreyez - Somewhere Over the Rainbow will suffer badly with only three chords. – Tim Apr 7 at 6:18

The I, IV, and V chords will certainly be enough to make a progression that subjectively sounds like it 'works', by most normal people's standards, under any melody that genuinely restricts itself to the major scale. As you say, you have all 7 notes of the key contained within your chord options (which allows any note in the melody to be a chord tone if you wish) and the transitions between all of those chords will sound very standard and subjectively acceptable to most.

As to whether it's possible to always make something that sounds good is more subjective - you might always be able to make something someone would like - but I think you might be in danger of boring yourself by using such a restricted palette of harmony.

I ask this because as I'm learning songs I know in different keys

It sounds a bit strange to be asking about which chords to use if you're learning songs you know. If you're learning songs you know, you (IMO) need to use the chords from the songs, or they won't sound right! You could restrict yourself to songs that do only use I, IV, V chords and play them in different keys though, if that's what you mean - in fact that sounds like a great exercise to me.

  • "If you're learning songs you know, you need to use the chords from the songs" -- I think that a lot of learners in early stages of playing by ear can fool themselves a bit into thinking that they have the right chords (maybe we can all do this a bit) under the 'if all you have is a hammer, everything sounds like a nail' theory of harmony. I am not sure whether the hammer or the nail is a I - IV - V progression ;) – David Bowling Apr 7 at 1:28
  • So I know about 50 songs (traditional and pop) that I've mainly figured by ear, and most I kept to C major on the piano. Mainly because it's easiest to play that scale. And I've harmonized these songs with all the chords (not just the primary ones). But now I'm trying to play these songs in other keys, so I'm dumbing down the songs I know to I IV V. and it doesn't sound half bad.. So far I haven't found a song that needed other chords. but I'm still in the middle of this. – foreyez Apr 7 at 1:31
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    @foreyez -- that actually sounds like a good exercise to me, but I wouldn't get too hung up on it. It will be real work, but you will gain a lot by learning to transpose the chords and melodies you know in, e.g. C Major, to all of the other keys. – David Bowling Apr 7 at 1:34
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    @foreyez: It is not nearly as true in minor keys. When a song uses the melodic minor scale, you frequently want IV and almost always need V instead of iv and v. When it sticks to the natural minor scale (or descends), you'll often find that VII is more useful than v. – Micah Apr 7 at 3:12
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    Go to holiday destinations - Canaries in particular, and you'll hear that most songs can be played using only I, IV and V! – Tim Apr 7 at 6:17

You could accompany a diatonic melody with just I. Bagpipes and hurdy-gurdys do it all the time. Going up a notch, yes the 'three chord trick' will enable an accompaniment to a diatonic melody that doesn't sound painful. But beware. Many simple songs are not diatonic in one key. And do you really want to merely avoid sounding dissonant, or do you want the RIGHT chords? I strongly suggest you move your goal from being able to play ALL songs with just a few chords to learning THIS particular song with the right ones. Then another...

  • I thought most or maybe all bagpipes played pentatonic scales. Am I wrong about that? – Todd Wilcox Apr 7 at 19:27
  • The question is - what are the right chords? There are so many options. In some cases, it is possible to know what the original composer chose, but in many cases like folk tunes it is whatever you think sounds good. I just wrote a piece based on Shenandoah and harmonized the tune once in minor and once in major. And I have no idea if they were the "intended" chords. Both sounded lovely, if I might say so myself. – Heather S. Apr 7 at 19:51
  • A Pentatonic scale can be looked at as a Major scale with some notes missing! – Laurence Payne Apr 8 at 13:06

In theory absolutely. This is basic harmonization theory 100. However, You have injected a bit of opinion into this question making it a little unfair. You ask if the harmonization will "sound good". That's a bit subjective. The I IV and V are enough to harmonize anything and you do have the inversions each of which have a different harmonic character.

But if you ask me it won't sound "good" until you start putting tri-tone substitutes in there, I IV V, bV, etc.

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