This month, Doctor Who triumphantly returned to our small screens, now on Disney+ and a new writing team. I’m a huge fan of the show, and I love how whacky and zany it can be. If you haven’t watched before, it’s a time travel show where the main character, called just “The Doctor” and their companions travel across the universe in time and space, usually getting into trouble. As a musician, I was keen to see what was presented last week, which was about the Beatles.

The Beatles and Doctor Who go way back, becoming popular around the same time and being large UK cultural exports to the rest of the world. The difference is, I suppose, the Beatles are still revered as ‘the best pop group of all time’, whereas only hardcore fans love Doctor Who to the same extent. There’s even a photo of John Lennon being surrounded by the iconic alien Daleks at a film festival.

This episode, The Devil’s Chord, opens with a piano teacher in 1925 playing the ominous sounding devil’s chord to his student. In real life, the devil’s chord is called a tritone, because it consists of three whole tones. It’s really actually an interval, not a chord, if we’re being specific. An interval is just the distance between 2 notes; e.g. F to B is a tritone, and C to G is a perfect fifth. A chord needs at least one more note; C, E, and G form the chord of C Major. Because there are only 12 semitones in an octave, and each musical scale is defined within an octave, there is only one tritone per diatonic scale (because when you count out the next 6 semitones, you end up back at the start. F to B is six semitones, and B to F is the next six semitones).

The tritone is referred to as the devil’s chord because it is very dissonant, and, so the mythos goes, in Medieval Times was banned by the Church for use in music because it would invoke the Devil. This episode takes that premise and runs with it, after playing the tritone (referred to as “the lost chord” because no-one else had played it before, apparently?), a magical god called Maestro appears, eats the music teacher, and then destroys music. This leads to the Beatles writing terrible music, and eventually all of humanity destroys itself because we couldn’t express our feelings in music. Can confirm, none of my music teachers were ever eaten by a magical God after playing a tritone. Go figure.

The idea of the Church banning the tritone is just that – a myth. Early Church singers would avoid singing the interval because it is really hard to sing dissonant tones. A perfect fifth is 7 semitones, and a perfect fourth is 5, both of which are easier to pitch or sing correctly than a tritone. Early Church music and the foundations of music it created (known as counterpoint, which form the basis for most European music moving forward) was very big on appropriate resolutions of intervals from dissonance to consonance. A staple of every Western music theory course is counterpoint: usually a line is provided for you (a series of notes) and you have to write an accompanying line following common practice. This means you have to appropriately resolve all dissonances and you can’t have too many consonances in a row (otherwise the piece is too boring). A reason why composers like Bach and Mozart are so revered is because of their contrapuntal skill; they could write parts that perfectly captured the right ratio of dissonance to consonance, “nice” sounds to “not nice” sounds.

Later in the episode, The Doctor realises he can banish Maestro by playing a secret chord. Now, a chord in music is quite specific. In classical music theory, a chord has usually three or four notes in it. A three note chord, as established, is the most basic block of a chord you can have; adding a fourth note usually provides an extra layer of dissonance to be resolved. Because there’s only 12 semitones in an octave, the biggest chord you can have is 12 notes (if you count octaves as doubling. The chord C-E-G-C, for example, is still a C Major chord, it just has two Cs instead of one. The chord C-E-G-B, however, is a C Major 7 chord, which would be more commonly seen as the dominant chord in the key of F major, and in common practice theory you could resolve it to an F Major chord). The Doctor begins playing the chord. “Ok,” I think to myself, expecting three notes before the special fourth one is played. Instead, the Doctor plays something like 7 notes and gets the 8th one wrong. 8 notes is a very dissonant chord indeed! Because the Doctor gets it wrong, a weirdly buff John Lennon and Paul McCartney have to save the day by playing the correct chord to save everyone. It’s possible the writers were just going for a chord with doubles of notes, but even still, the secret chord could be boiled down to at most 3 or 4 notes. Don’t play the rest, that’s more likely to go bad!

Overall, it’s a fun episode, and there’s some fun bits of music theory which are actually relevant sprinkled in (the apocalyptic future without music is ideal for Maestro because of its “aeolian tones” or tones which are produced by wind blowing through things). It’s fun to have a Doctor Who episode that I can critique in an academic way, since most of them have nothing to do with music. Is this how artists felt during the Vincent van Gogh episode?

What other tidbits did you notice in this episode? Any other musical topics you’d like me to elaborate on? Let me know in the comments below.