Consonance + Dissonance - What makes something sound "bad"?

How does this compare to this? Does one sound better than the other? If so, why? Let's explore together. Hi everyone and welcome to Music Theories, where I explain and analyze all topics related to pop music, music theory, and music history. This video is part of a series I'm making, exploring the fundamentals of music and music theory. Please check out the first two episodes, linked down below and up in the i, From here, we'll be moving into things like melody, chord progressions, rhythm, and so on. So be sure to subscribe and hit the notification bell if you want to keep up with what's to come. In the last episode of this series, I discussed what's called the overtone series. Just to refresh, overtones or harmonics are frequencies that we hear within a fundamental pitch. The overtone series is the foundation of how we understand and communicate western music. Which ultimately is what we know as music theory. When we discussed this topic, we were specifically referring to what happens when you play one pitch. But what happens when you play more than one pitch? Well, things get complicated. The other day, a student asked me, why have we been using the same musical scale for hundreds of years? Can't they come up with something different? And while it's not entirely accurate, I thought it was a great question. To begin to answer that, we first have to look at what's called consonance and dissonance. This is how we classify certain sounds. It's how we decide what sounds good and what doesn't. But who decides? Interestingly enough, what falls into either category has changed over the years, or should I say centuries. It's important to note as we move forward, that notes that sound stable or pleasing can differ from region to region, culture to culture, and even time period to time period. But for this video, I'll be focusing on what I know personally, which is Western music. One could argue that even in Western music, consonance and dissonance can be something that is subjective. However, there is a definitive system to decide which is which, based on Pythagoras' mathematical findings, which I talked about in the previous segment. The mathematical breakdown for each can be described using ratios, which is not something I'm going to get too deep into, but I have a really interesting visual to show you that might help you get the idea. But overall, it's essentially based on how the fundamental and its overtones interact with that of another's. The distance between one note to another is called an interval. We measure this distance by the number of half steps between them. Western music often considers the half step, or the minor second interval, to be the smallest distance between two notes. Both the guitar and the piano are set up in half steps. I want to point out that there are, in fact, smaller intervals, but we typically don't use them in Western music theory, so you don't need to worry about those. Let's discuss which of our intervals are considered what and why, starting with consonants. But first, I want to quickly mention something called interference. This will make our visuals a little easier to understand. When two waves are combined together, the effect is the addition of the amplitudes of the individual waves. This is very clear when we combine two unison waves. For simplicity's sake, we will consider everything above this line to be positive, and everything below that line to be negative. If the phase of two waves at any point are both positive, they will reinforce each other. This is called constructive interference. If the phase of one of the waves is negative and the other is positive, the waves will interfere destructively. This is called destructive interference. With that out of the way, let's look at some examples. The word consonants typically refers to notes that sound agreeable or pleasing when played together. They can also be described as stable. Musicians typically use this term to describe intervals that don't sound like they need to be resolved. They sound complete on their own. We can listen to what these intervals sound like, but let's also take a look at how they interact. For example, let's look at the octave or the perfect eighth. As we discussed in this video, a fundamental pitch's octave has twice the frequency. So if we take a C4 and we double it, we get a C5, a higher version of the same note. Our sine waves show this as well, as you can see. As mentioned last time, aside from the octave, the most stable interval is what's called the perfect fifth. This is the three-to-two ratio around which the entire Western music theory is centered. What this ratio means is that every two waves of the fundamental accounts for three waves of the fifth, as you can see here. The perfect fifth is made up of seven half steps, and it sounds like this. The next interval on the stability spectrum is what's called a perfect fourth. This one has a four-to-three ratio, as we can see here. The perfect fourth is made up of five half steps. These intervals, along with the octave, are called perfect because of their stability, or rather, the way that their overtones interact and blend so evenly. So if you're like me and you've wondered why they're not called major, that's why. That said, there are some caveats with the perfect fourth that we can get into more as we go along. But long story short, it can be considered consonant or dissonant based on its context within the music. The other intervals considered to be imperfect consonances include the minor third, the major third, the minor sixth, and the major sixth. The ratios of these intervals feel stable because the frequencies of the two fundamental pitches interact with each other somewhat evenly. And when they don't interact evenly, that's when you get what we call dissonance. The word dissonance usually refers to notes that sound unpleasant, tense, or unstable when played together. These are two notes that will feel unresolved, like they need to go somewhere else to feel complete. The first example of this is a minor second, which is equivalent to one half step. Check out the waveform on this one. They're so similar to each other that they actually create this interesting pattern where they cancel each other out. What we hear is them beating against each other to create this pulsating sound. Following that is the major second, the tritone, the minor seventh, and the major seventh. On top of these overtones rubbing against one another, we've been conditioned to expect them to resolve. For this reason, music that uses primarily dissonant chords without much resolution tends to be avant-garde and difficult for a lot of people to listen to. Now, if you're wondering why we even use dissonant intervals when they're thought to sound bad, you can think of it like life. Dissonance does not equal bad. It depends on culture and context. We need dissonant intervals to make music more exciting, more predictable, and more satisfying. These tense moments make the relaxing ones feel that much better. This idea of tension and release translates through many areas of life, including music. And this idea will be very important as we move into things like melody and chord progressions. Additionally, the way the information was presented in this video might make it seem like consonance and dissonance is something that's absolute. What I want us to keep in mind, however, is that it really isn't quite that simple. This explanation is in reference to how music is processed and analyzed conventionally, just as Western music theory is only one way to understand music. So with all that said, we'll stop here for today. Make sure to subscribe and hit the bell to be the first to know when the next episode is out. Feel free to ask any clarifying questions down below. I'm looking forward to the next one. Bye!