I’m walking the kids to the bus-stop when my 9-year-old, Sophia, inquires, “You know how you can hear songs in your head?”
“Uh-huh.” (The song on endless loop in my head at that moment is, annoyingly, the children’s song Do you know the muffin man?)
“Well, can you hear two notes at once in your head?”
I pause to imagine a perfect fifth, which, true to my early 80’s musical training, always sounds like the opening notes of the Chariots of Fire theme. “Yep, I can hear two notes at once. Or more. I can hear a major triad. Or a minor triad.”
The kids both look as if they’re listening to something I can’t hear, and, nodding, they confirm that they too can hear triads in their minds. Sophia still looks puzzled, though. She cocks her head to the side and asks, “We can’t sing two notes at once, so why can we hear two notes at once?”
As with many questions the kids ask me, I’ve never thought about that before. What the kids and I are discussing (and doing) is a form of auditory imagery. I’ve blogged before about involuntary musical imagery, or earworms, but what we’re talking about here is voluntary musical imagery, or what many musicians call audiation, the purposeful mental reconstruction of musical sounds. The ability to audiate is an important skill for musicians. If we can hear a song in our heads, we can use this representation to help us learn how to play it. If we don’t know how a song “goes” then it’s much harder to tell if we’re playing incorrect notes. Audiation is especially useful during sight-reading.
But what about the two-notes-at-once question? Our vocal cords are not able to produce more than one note at a time, but that doesn’t mean our brains can’t represent two (or more) notes at once. In fact, research has shown that when we hear music in our minds, the parts of the brain that are activated are very similar to those activated when we hear music.
It’s tricky to study audiation because there is no systematic way to prove that it is actually occuring – it’s all in the person’s mind, after all. A classic type of study was conducted by Kraemer and colleagues in 2005. They put subjects into an fMRI scanner and played them excerpts of familiar and unfamiliar songs. This activated the primary auditory cortex and auditory association cortex of the listeners. To induce audiation, the songs were then replayed with silent gaps replacing short sections of music. In the familiar songs, the silent gaps led to activation of these auditory areas. The participants confirmed that during the gaps in familiar songs, they could hear a continuation of the music in their mind. The researchers concluded that the activation in the auditory areas of cortex was the source of the audiated songs.
Because we can hear two notes at once, we can also imagine two notes at once, using our versatile auditory association cortex.
Kraemer DJM, Macrae CN, Green AE, Kelley WM. (2005) Musical imagery: sound of silence activates auditory cortex. Nature 434(7030):158.