Issue 12 - Not all canons are rounds!

This Sunday's prelude is based upon the sermon hymn, LBW 206, "Lord, Who the Night You Were Betrayed". The hymn tune was composed by Orlando Gibbons (1583-1625), a famous composer and organist at Westminster Abbey and the Chapel Royal. David Cherwien composed the organ chorale prelude based upon that tune.

This prelude setting of the hymn is a canon. While the right hand plays a soft accompaniment of running triplets, the left hand and pedal play the melody of the hymn in canon. It's a really beautiful arrangement, very peaceful - and the canon creates a delicate duet between the left hand and pedal.

So - what is a canon? Most simply put - a canon has a melodic leader and a imitating follower. The leader (in this case, the left hand) begins "singing" the melody and follower (in this case, the pedal) sings the same melody but one measure later. We've all sung rounds like "Row, row, row your boat"... well, a round is the simplest form of a canon. In a round, the follower voices sing the exact same melody as the leader... round and round it goes. All rounds are canons.

However, NOT all canons are rounds. Canons can be much more complicated than rounds. For instance, in a canon, the melody may repeat at an interval four or five notes higher than the original melody. Or a canon may have the follower invert the melody (meaning that if the leader sings five climbing notes, the follower would sing five descending notes instead). Or a canon can be in retrograde (meaning that the follower would sing the melody backwards!). The crab canon is where the leader and follower sing at the same time but the follower is in retrograde. Mensuration canons are where the follower's melody may be lengthened or shortened by some proportion of the original (for instance, quarter notes might become half notes for the follower).

Of course I had to write some canons while in school. It is NOT easy. To compose a melody that's beautiful and interesting, but will also work in canon is quite difficult. And to compose a canon that would work in inversion, retrograde, mensuration --- well, I don't think I ever succeeded in writing one of those!

Composers of the Renaissance (like Gibbons) embraced the challenge of canons and even enjoyed writing what are known as Puzzle Canons. This is where only the leader's melody is written. The composer will then give a clue as to what kind of canon to perform. In Guillaume Dufay's mass L'homme Armé, he gives the clue: Cancer eat plenis et redeat medius (Let the crab proceed full and return half). So, the melody is first performed in full note values and retrograde (since it's a crab), then in halved values and retrograde (which would mean forward motion since retrograde of retrograde would be forward).

No worries, the prelude is a simple canon. You'll easily be able to discern the imitating melody. In fact, one phrase of the melody doesn't work in canon without becoming extremely dissonant --- so Cherwien just breaks away from the canon and sets it in chorale style. Once that phrase is over, it's back to the canon to end the piece. Enjoy!

(Image: "Crab Canon" by M.C. Escher)