# Parallel keys



## Aurelian

A strictly followed practice is using the parallel key to contrast the mood of a previous movement or within a movement. Examples:

_Ronda Alla Turca_ alternates between A minor and A major.
Mendelssohn's Violin Concerto and Tchaikovsky's 5th Symphony begin in E minor and end in E major.

But, why is this practice followed so strictly? Would _Ronda Alla Turca_ alternating between A minor and D major be that bad?


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## BabyGiraffe

You are free to do anything you like in composition.

"Would Ronda Alla Turca alternating between A minor and D major be that bad? "

Try recomposing it/create variations to your liking to hear how it would sound, it's not a bad compositional exercise.

About stylistic norms - they are not "rules", just observations, noticed by musicologists. Change a few rules and you have new style or musical form.


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## hammeredklavier

The slow movement of Beethoven string quartet Op.132 "Heiliger dankgesang" alternates slow sections in a modal F with faster sections, "Neue kraft fuhlend" in D.
Chopin ballade No.2 in F major alternates between calm, lyrical F major sections with fiery A minor "allegro con fuoco" sections.

It seems that the practice of switching between parallel keys was more strict in the Baroque/Classical period. I find a lot of relative major/minor relationships as well, 
take for example, in Mozart's Salzburg masses before 1777, (not the newly-fashioned C major ones where he deployed "symphonic devices", such as K.257, K.317 )
the agnus dei movements initially start in the relative minor, end with dona nobis pacem in the original keys of the masses.
K.192: agnus dei (D minor) - dona nobis pacem (F major)
K.194: agnus dei (B minor) - dona nobis pacem (D major)
K.275: agnus dei (G minor) - dona nobis pacem (B flat major)
also there is a special case;
K.337: benedictus (fugue in A minor) - hosanna excelsis (C major; same material as sanctus)


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## Phil loves classical

The idea is to use the same tonic. See here, Rondo alla Turca already alternates with relative major and minor chords within sections already. Between A minor and C major, and A major and F# minor. The use of the same tonic ties things together to some effect that a modulation to another key couldn't.


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## Bwv 1080

Perhaps alla Turka gives a hint? Turkish music is not known for modulations to remote keys


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