What is…Pitch?

Stephen Johnson gets to grips with classical music's technical terms

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Pitch refers to how high or low a musical note is.

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The composer Glazunov hated going to Moscow. It wasn’t the arduous journey, or the ‘direct’ manners of the Muscovites that pained him. It was that the A to which the Moscow musicians tuned was minutely sharper than the A he knew in his native St Petersburg. It was agony for him.  

Confronted with stories like that, most of us would think ourselves unmusical clods in comparison. But unless we had a pretty refined sense of pitch, we wouldn’t be able to catch the minute inflexions in the speech of relatives and friends that can tell us so much more than their words.

Nor would music say so much to us: along with rhythm and tone-colour, the relationship between notes is a fundamental ingredient of music. 

Take the two emphatic chords that open Beethoven’s Eroica Symphony. If the top note in those chords, G, were just a semitone flatter, the character of that opening would be changed irrevocably.

Listeners familiar with Western ‘equal temperament’ tuning – and thanks to the universality of recorded music that’s just about everybody – would no longer experience those chords as bright, positive, joyous, but tenser, darker, more ominous.  

Or take jazz. Most listeners know intuitively what a ‘blue note’ is, and will probably only have to hear the term to remember the kind of physical and emotional effect produced by that minute flattening of the pitch. In most cases it’s much narrower than the semitonal modification that would radically alter the character of Beethoven’s Eroica

The story of our modern ‘equal’ tuning system – in which tones and semitones are more or less equal throughout the pitch universe – is long and complicated. But at least until the mid-18th century the tuning of a scale was much more variable: closer to the ‘natural’ overtones that shimmer like a halo around any note struck, bowed, blown or sung.

In terms of physics, these overtones obey a strict proportional relationship, but to our conditioned ears they jar. The horn solo that introduces Britten’s Serenade for tenor, horn and strings is tuned to these natural overtones, and how gloriously ‘wrong’ some of them sound – and how important that ‘wrongness’ is to the character of the music that follows!

So even if you’ve never given pitch relations a moment’s thought, you’ve probably been stirred by them and the patterns they form as often as you’ve responded to the meanings in words and phrases.

We left the composer Glazunov in Moscow, suffering agonies because the Moscow ‘A’ was minutely sharper than the St Petersburg ‘A’ he was used to. He, though, had it good – improved communications in his day meant that musicians were able to travel much more, which led to increasing standardisation in the tuning of the concert ‘A’.

It also led to standardisation of relative tuning: the distance between the notes of the major, minor or chromatic scales.

Just imagine Glazunov’s pain if he’d been able to travel back in time. The old ‘natural’ tuning, based on the halo of ‘overtones’ which reverberate above any struck, blown or bowed note, may have made sense to Pythagoras, who argued that relationship between these overtones revealed nothing less than the fundamental harmony of the universe.

But to our ears, they can sound weirdly out of tune – if you try tuning a keyboard using natural overtones as your guide, you will end up with something which sounds relatively secure in, say, the basic C major, but the further you get from C major, the weirder it sounds.

Baroque composers exploited this to heighten expressive effects.

When Handel wanted to depict the agonies of Christ in Messiah, or Vivaldi the asperities of ‘Winter’ in The Four Seasons, both chose the key of F minor, which in most early 18th-century tunings would have sounded relatively out of tune: the harshness of the harmonies and jaggedness of the melodic lines would have intensified spectacularly. 

As the keyboard rose in popularity in the 17th and 18th centuries, the need for standardisation of relative tuning became more acute.

Bach’s Well-Tempered Clavier, which features all 24 major and minor keys, was written to take advantage of this ‘equal temperament’, in which the distance between two adjacent notes is more-or-less equal wherever it is on the keyboard.

But perfectly ‘equal’ temperament was rare; there were lots of subtly different versions of it. So if poor Glazunov had been catapulted back into 18th-century Europe he would have found even more painful divergence from city to city, plus local differences in the familiar major and minor scales.

Moreover, the ‘average’ ‘A’ of the period was probably around a semitone flatter than Glazunov’s Moscow or St Petersburg ‘A’s. There are times when it’s an advantage not to have too ‘good’ an ear.

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This article was first published in the April/May 2013 issue of BBC Music Magazine