Our today's selection for sight-reading is Medio Registro Vasso by Pablo Bruna (1611-1679), an important Spanish early Baroque composer, notable for his blindness.
Most of his works are in the form of tiento de medio registro (a Spanish version of the polyphonic ricercar for organs with divided keyboards). The divided keyboard was a typical feature of the Spanish organs of the day (the division was at middle C/C#). This meant that using only one keyboard, an organist could play with two distinct sounds - one for the bass (up to middle C) and one for the treble (from middle C# upward).
Exactly such piece is Medio Registro Vasso. The highest C in the bass is reached several times (in measures 25, 85, and 114). The right hand part does not descend lower than C# (in measures 19 and 66-68).
This tiento is written in the mode of G and starts with the subject which is 4 measures long in 4/4 meter.
Here's the plan of this tiento:
1. (m. 1) Subject in the tonic (alto).
2. (m. 3) Answer in the dominant (tenor).
3. (m. 7) Answer in the dominant (soprano).
4. (m. 14) Answer in the dominant (bass).
5. (m. 18) Subject in the tonic (bass) with diminutions.
6. (m. 24) Subject in the tonic (bass). After that, the tiento develops like a free fantasia with a highly ornamented bass.
7. (m. 55) Fragment of the subject in the tonic (bass).
8. (m. 58) Fragment of the answer in the dominant (bass).
9. (m. 61) Fragment of the subject in the relative minor of the subdominant (bass).
10. (m. 63) Change of meter (3/2).
From that point, sometimes the music moves in 6/4 meter (compare m. 63 with 65). In m. 63, there are three half notes in the right hand part and in m. 65 - two dotted half notes. That's the difference between 3/2 and 6/4 meters.
The same thing is in m. 104-107 (3/2 meter) and from m. 108 (6/4 meter). The duple meter returns only at the final cadence (m. 129). When playing this piece, you have to be conscious of these meter changes - in 3/2, count "1 and 2 and 3 and" while in 6/4, count "1, 2, 3, 4, 5, 6", stressing 1 and 4.
As I played this piece today, I found that the tricky places would be:
1. (m. 13) Preparation for the bass entrance - including the movement of the tenor to the right hand part and keeping it tied-over the bar line (G) while the alto plays B-A separately. Remember to articulate.
2. From that point, the main difficulty with the right hand part will be articulation - making sure the syncopations and tied-over notes are held precisely and the other parts are played with articulation. The solution to this problem is to play slowly enough so as to notice the different rhythms of the three upper parts.
3. (m. 63) Change of meter. Refer to the counting ideas above (from 3/2 to 6/4 back and forth).
4. (m. 100 onward) Fast eighth note movement in the left hand part.
5. (m. 104 to 107) Change the counting to 3/2.
6. (m. 124) Unexpected dominant 6/5 chord at the second half of the measure.
7. (m. 129) Change of meter.
Take a slow tempo and use articulate legato touch throughout. If you can't play both hands together comfortably, work on separate hand parts. Since not too many organists nowadays have access to organs with divided keyboards, most people will have to play it on a two manual organ with the bass part on the solo registration.
Here's the score for printing, if you want to play this rhythmically interesting tiento.