Transposition is a musical term for moving notes higher or lower to change key. As an arranger, the question I'm asked the most is: "Why is the music in this key?" Though more often than not, questions are phrased as expletives, "Pachelbel wrote his Canon in D minor for a reason, get a clue!"
So why do arrangers transpose? Why not keep everything in it's original key and for that matter why don't composers always write in C, as it has no flats or sharps?
Choosing the key of a piece is somewhat like choosing a seat in an airplane. Though all the seats are sort of the same, everyone has preferences, for various reasons.
Perhaps it's a day flight and you want to look at things, so you choose a window seat. You may want to be near the emergency exit because you have a fear of flying, or you may want to be on an aisle because you like to get up a lot. Maybe you are traveling with your kids, and want to be in the middle seat to referee. If you are trying to make a connector flight, you may want to be near the main exit so you can disembark as soon as possible. Whatever the reason, the more you travel, the more confident you become on your choice of seats, and so it is with music. Transposition, then, is akin to the act of choosing your seat on a plane and also sometimes, switching seats in mid-flight.
When I'm choosing the key for a piece these are some of my considerations:
- Range: That's how high and low the primary instrument can play. Usually I am arranging for flute. The lowest note it can play is C and the highest is C two octaves up. I like a buffer, so I rarely have music that touches the extremes. A vocal range is smaller than the flute range, whereas, piano and violin have much greater ranges. I may have to transpose the whole piece up or down if some of the notes fall outside the range of the primary instrument.
- Key Signature: That's the sharps or flats. Band instruments tune to Bb and people that play in bands tend to see more flats. Orchestral instruments tune to A and players tend to see more sharps. Piano is actually easier to play with a few flats or sharps in the key signature because it gives your fingers some grounding. I find Eb the easiest key on Piano, C the easiest on guitar, and the key of G the easiest on flute. Generally, I prefer C, F, Bb, Eb, G, D, and A as those all have the least sharps or flats and key signatures you encounter the most. It comes down to playability. A piece may fall nicely in a range, but if the key signature is C# or something unusual, it makes the music unnecessarily difficult to play.
- Accidentals: These are notes outside the key and I think about how difficult they would be to play for the particular instrument.
- Instrument idiosyncrasies: On flute Bb - C requires moving one finger, so if you have fast notes between Bb and C it's easy on flute. For trombone Bb is in 1st position and C is 6th position, so fast notes are impossible. If I was transposing a piece written for flute to trombone, I would put it in a key that avoided that particularly difficult note switch.
- Backing instruments: If you end up transposing up a 7th, which is pretty common, some instruments, particularly the bass and piano can then be too high, and if you transpose them down a 5th, to stay in the same key, they are too low. Sometimes I feel like Goldilocks trying to find the balance between having the music sound right and still be in a key is playable for the solo instrument.
- Instrument Key: Many instruments, particularly band instruments are not keyed in C, but rather Bb, Eb, F or some such crazy thing. That means you have to transpose all those instruments to different keys and sometimes the resulting key can be horrific to play, with a difficult key signature, outside the playable range, or creating very difficult note changes. If you are arranging for a group, you then have to take "playability" and "overall sound" into account for everyone, so generally, nobody is happy.
Transposition (changing key) in mid-song is done for dramatic reasons. It's like SUDDENLY CHANGING TO ALL CAPS TO MAKE A POINT! It can be very effective, though if you do it too much it simply becomes annoying. When to have a key change is usually more the job of the composer, though on occasion, when I'm arranging something, I will throw in a key change because the song is kind of repetitive and I have become bored. With this song "Canada Ghost Lover", I transposed it through all 12 major keys as a learning exercise.
This music plane of ours has 24 seats. Twelve major and 12 minor. There are also blues scales, pentatonic, modes, chromatic and micro-tonal scales, but for this blog, I have checked them into the baggage section, so we can ignore their existence.
If you want to change seats (transpose) there are some easy moves and some difficult moves. Some will sound awkward as you climb over other passengers and only if you really want to draw attention to yourself do you choose those. Transposing to a relative minor is like switching to the seat beside you, pretty easy.
Transposing in the circle of 5ths, as I did with "Canada Ghost Lover," is probably the smoothest way and the most common. In circle of 5ths transposition, the dominant of the scale, becomes the tonic of the next scale and our ears adjust very naturally.
When I'm arranging a song that contains a key change or two, I have to transpose those key changes as well so the problems start multiplying and again you end up in a place where nobody is happy. As our music plane takes off, everyone hates their seats, the wifi doesn't work, the man in front has reclined into your lap, the kid behind starts randomly kicking your seat and you've seen the movie.