The very first thing you have to do if you want to play your hymn in another key is to understand the original key first. In other words, there is no point in trying to blindly copy note by note, interval by interval the chords of the hymn in a different key unless you know how it is put together and unless you understand the meaning of each note in your hymn. There are a few possible techniques how to go about this and in this post I'll share with you one of my favorite and simple ways in hymn transposition.
In order to understand your hymn, first you have to determine what the key of the hymn is. You can do this easily by looking at the couple of things: the accidentals next to the treble and the bass clefs, and the ending note in the bass part.
If you know the system of circle of fifths, the accidentals will tell you the pair of paralel major and minor keys with the same number of accidentals. For example, if you see 3 flats next to the clef, this means your hymn might be written in the key of E flat major or C minor.
To determine the key exactly, look at the last note in the bass part, as it is most likely the first scale degree in that key. For example, if your bass note is E flat, then the key is E flat major. If it's C - then it's C minor.
Once you know what the original key of the hymn is, write in the scale degree numbers for each note in each part with pencil. This is relatively easy to do except in places where the tune moves to another key (modulation) which you can see from the new accidentals.
Remember that in the minor key, there is often a raised 7th scale degree present (harmonic minor mode). In the case of modulation, switch to the scale degrees of the new key for a moment.
By having written in scale degree numbers you have prepared yourself for the actual transposition of the hymn. Now I recommend you transpose your hymn in the order of ascending number of accidentals. First, start with C major or A minor which don't have any accidentals.
Obviously, hymns in the major key will have to be transposed to major key only and hymns written in the minor key will work in the minor key but not in major.
After C major or A minor play it in the key with one sharp and one flat. Later - in the key with two sharps and two flats and so on until you reach 7 sharps (C sharp major or A sharp minor) and 7 flats (C flat major or A flat minor).
Remember this rule - the scale degrees of the original key you have written for each note must match with the scale degrees of the destination key.
A word of caution: if you are new to transposition exercises, don't try to play all four parts together in the new key. To make this process as easy and as enjoyable as possible, just like while learning a real organ piece, first practice each part separately. Then - combinations of two voices, three voices and only then - the entire four-part texture.
The focus here is on the word PRACTICE. It means you should aim for at least three correct and fluent repetitions in a row of each part or combination before advancing to the next one. Take a slow but steady tempo. Practice short fragments of one hymn phrase at a time before putting them together, if you need to.
Although it may seem like a bit complicated process, the above advice is all you need to do in order to transpose a hymn on the organ. Be patient, enjoy each moment and know that while practicing transposition, you are doing things that at least 80 percent of organists have never had the courage to attempt but only dream about.
Give it a try today with the hymn of your choice.
By the way, do you want to learn my special powerful techniques which help me to master any piece of organ music up to 10 times faster? If so, download my video Organ Practice Guide.