# How do sound waves work that make certain intervals sound good?

I'm learning waves in my physics class and I was wondering, how do sound waves work that make certain intervals sound good. Why does a M3/P4/P5 sound really good while m2/M2 sound (kind of) bad?

• Duplicate on Music SE: Why do some intervals sound better than others? Feb 28, 2016 at 11:22
• Can you clarify whether you mean harmonic intervals (notes played simultaneously) or melodic intervals (played consecutively)? Also, i think you are probably meaning consonant and dissonant rather than good or bad. For example, jazz is loaded with dissonant intervals like tritones and minor 2nds but it sounds good to me.
– Tom
Feb 28, 2016 at 23:58
• Oops I accidently deleted a sentence from my original post, but I meant harmonic. And yeah I'm meaning consonant and dissonant (didn't know those words existed). Yeah they do sound good to me (hard to explain, it's like it clashes and can be heard as a mistake if used incorrectly), but I'm confused about why some of these intervals are consonant or dissonant. Zenith's answer comment helped a lot though. Feb 29, 2016 at 3:59

Simple frequency intervals generally sound good. Our auditory processing parts of our brains appreciate simple relationships. A perfect fourth has a 4:3 frequency ratio and a diminished fifth (arguably not a very pleasant interval) has a 45:32 frequency ratio.

https://en.wikipedia.org/wiki/Interval_ratio

https://en.wikipedia.org/wiki/Interval_(music)

If you really wanna go to the depths of this, I highly recommend "How Music Really Works", a great book:

http://howmusicreallyworks.com/

Have fun!

Hens Zimmerman

• I disagree strongly with this. Simple frequency intervals sound simple, not good. Complex frequency intervals sound complex, not bad. The value judgement comes from how used to those intervals you are, depending on what musical heritage you grew up in. Feb 27, 2016 at 7:45
• @SimonWhite I think the argument you're making is really over the words "good" and "bad." Those are subjective terms so one person's good is another person's bad. I think the op is really referring to consonant vs dissonant.
– Tom
Feb 28, 2016 at 23:49

Particular intervals don’t sound good — they sound familiar.

It all comes down to what you are used to. Which intervals were used in most of the music you have heard in your life, depending on its musical heritage. How trained your ear is to appreciate various intervals.

If you grew up in Texas and have listened to country music all your life, the intervals that are common in country music will sound good to you. If you grew up in Turkey listening to traditional Turkish music, you would prefer the intervals that are common in Turkish music. Then if you traveled, the unfamiliar music you encounter might sound jarring and dissonant to you at first, but pretty soon your ear is trained to appreciate that it is not bad, it is just different. You may grow to like it more than the music you grew up with.

A well-trained ear won’t hear any interval as bad — just different. Once your ear is well-trained you might seek out even more new intervals. For example, listening to music concrete or music that is made on historical instruments.

• Wow. That makes perfect sense. What I've found is that intervals on the low end of the piano sound weird even though they sound fine in the upper octaves. I realized that they sound off on the low end because the frequencies are low enough that I can perceive the beats between the frequencies of the notes. I guess that's why some cultures like microtonal music while in sound bad in western culture. Also I've realized that I have appreciated m2/M2s more when I actually began to compose music than when I just played and listened; they were rare and so I didn't see/hear it as often. Feb 28, 2016 at 6:05
• I think this answer makes sense for melodic intervals. Eastern music uses different scales than western and that's obviously a learned response. I don't think the same is true for harmonic intervals, though. As the answer zenith linked to above shows, the simplicity of the waveform due to the frequency ratios plays a part in perception. I think how consonant or dissonant something sounds is fairly universal across cultures
– Tom
Feb 28, 2016 at 23:45