Earlier today, Coca-Cola teamed up with Rock Mafia and a diverse array of emerging artists from around the world to release what might be the world’s happiest song.

To help understand the DNA of a happy song, we spoke with Dr. Adrian North -- an Australian music psychologist who consulted with Rock Mafia during the creative process. Dr. North is the author of How to Produce Happy Music.

You have a PhD. in music psychology, a discipline most people have probably never heard of. Can you tell us a bit about your research and expertise?

Rather than focus on specific pieces of music, per se, music psychologists look at the underlying characteristics that lead to certain types of emotional response. For the last several years, my research has focused on how and where we listen to music. Technology has increasingly contextualised music, and we’ve found that’s an important part of people’s responses, too.

Mobile devices, online streaming services and other technologies have clearly impacted the way we consume and share music. How have they changed the way we process music emotionally?

Before, listening to music was a passive, receptive process. It wasn’t in any way interactive. Now we have access to just about any piece of music that’s ever been recorded. We can listen to whatever we want, whenever we want and where ever we want. Rather than being passive recipients of music, we’re now active consumers of music.

One big factor is the degree of choice and control we now have. What distinguishes the music we enjoy hearing in public -- in elevators, hotel lobbies or stores, for example -- from music we don’t enjoy hearing is when we have some control over it. Now, when you ride the subway or the bus, you can look around and see everyone sitting there with earbuds, staring at their phones. It’s become this little auditory bubble -- this mini-world in which, even though you’re out in public, you can control. That’s the biggest change that has taken place.

What makes music happy?

It’s driven by two factors: How much you like or dislike a piece of music, and secondly, how arousing it is… to what extent it gives you a physiological jolt. You can gauge a listener’s emotional response to a piece of music by knowing if he or she likes or dislikes it, and if it’s arousing or not.

You can like calm music, but it doesn’t arouse you. And with unsettling or scary music, people may not like it, but it’s highly arousing. Happy music gives you something you like but also tends to be arousing.

So can only up-tempo music be considered happy?

Theory says that the more up-tempo the music, the happier it will be. But it’s all relative. Just because one person finds a piece of music arousing -- which means it has the potential to be happy -- doesn’t mean someone else will. But generally, yes, as music becomes faster it becomes happier.

Is the definition of happy music universal, or have you found geographic and demographic nuances in your research?

Yes and no. Within a region where musical compasses overlap, yes, to an extent. But if you study cultures that are radically different, that language starts to break down. A great example is Indonesian funeral music, which to Western ears actually sounds quite jolly. We know more generally that people use music for different reasons. Males, for example, are more likely to use music to try to impress others. Whereas females are more likely to use music for emotional regulation. My research on relationships reveals that when males choose who to date, they want their partner to share their musical preferences. Females, on the other hand, could care less.

So has the definition of “happy” music evolved over time? 

It has, but in a fairly predictable fashion. It goes back to the concept of arousal. If a composer keeps playing people the same music, they’ll get bored and stop listening. Composers in any genre deal with this in the short term by keeping the audience’s attention by making music more and more arousing. A classic example is heavy metal, which started out in the 1980s at a normal tempo. By the mid-90s, thrash metal had emerged and sped up the tempo considerably. Metal artists have clearly tried to make their music more extreme to keep fans’ attention. But you can only go so far with that. Music can only go so fast before it stops being music and becomes random noise. That’s a point in time in any genre where you see this flip. Composers have to be innovative in different ways. That’s when you tend to see periods of real creativity.

What about lyrics? What role do words play in a song’s happiness quotient?

Music psychologists have practically stopped studying lyrics because people’s attachment to them is so idiosyncratic that it almost defies scientific analysis. In general, people don’t really get lyrics. What might be considered explicit in meaning remains a mystery to most people. One interesting piece of research examined the Billboard Top 100 from about 1955 to about 1990 and looked at the amount of “pessimistic rumination” in those songs. In other words, the expense to which they explored sad stuff over happy stuff. The researchers found that by looking at the amount of pessimistic rumination over time, you could predict changes in American GDP with a six-month time lead. This research showed that when we listen to music all day in various shapes and forms, it tends to seep into our unconscious thinking. And that affects our more general level of optimism which, in turn, seems to affect the economy. So happy music actually seem to make the world not only a happier place, but also a richer one.