Bahamas’s Caught Me Thinking and the Shepard Tone

With a candle in my hand and squeezed onto a picnic blanket full of friends, I’ll soon be spending another August weekend at the Edmonton Folk Festival. Tickets sold out in an hour on Friday morning, and I’m pretty pleased to have a pair. One of the acts I’m most looking forward to this year is Bahamas, the stage name of Toronto guitarist and singer Afie Jurvanen. Once a regular supporting player for Feist, his second solo album Barchords was released in February, much anticipated after his Polaris Prize nominated debut.

As Bahamas, he has created fascinating mix of breezy light songs that pulse with an undercurrent of melancholy. They seem almost forgettable at first and then grab hold of something and don’t let go. Part of the appeal is his rich soft voice. There’s also his attention to detail in how every plucked string sounds, often using vintage guitars from the 50s and 60s to get just the right tone. This week’s song, though, is even more clever than that.

Caught Me Thinking has a boppy almost toe-tapping feel. It might make you smile if the lyrics weren’t so utterly filled with grief. Despite the catchiness, it guts me every time I listen to it. The brilliant device that makes it work is found in the opening seconds. A handful of notes lead into a strummed chord. The chord doesn’t fade though, it starts to rise. And rise. And rise. And yet, when it ends, the chord that follows doesn’t seem significantly lower in pitch.

It’s an effect called the Shepard Tone, name after cognitive psychologist Roger Shepard. The effect works by using paired notes that are an octave apart (a middle C and a high C for example). Both are played at the same time with the higher one louder than the lower. Then each slowly rises in pitch. As they rise, though, they trade volume: the lower notes gets gradually louder as it gets higher, the higher note gradually softer. Around the time that both have gone up by an octave (the middle C has become a high C) the higher note has faded out completely and returns quietly an octave lower, which turns out to be exactly where the other note started (e.g, Middle C). The whole process continues like this over and over.

It’s like playing slinky in your hands: you raise one hand up until the slinky falls into your other hand below. Then you slowly raise that hand until the slinky again falls into your other hand, which you’ve dropped down below. You can play forever raising and dropping one hand after another.

The impression the Shepard Tone gives is of a sound rising and rising, but because the top note always fades out and begins again the octave lower, it never goes anywhere. It feels like it could go up endlessly.  The effect is an unnerving aural vertigo.

One of my favourite examples of the Shepard Tone is in the opening of NBC’s classic sci-fi radio drama X minus One, the vacuum of space delivered straight to your gut though the magic of radio.

In Caught Me Thinking, Bahamas uses it cleverly to make what could be a light and cheery song, some much deeper and more unnerving. I don’t know if he’ll be able to recreate that live at Folk Fest, but I know I’ll be able to close my eyes and hear it that way.

Author: mcshanahan

Science education researcher and writer

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