The prelude is composed in the Italian style, similar to Frescobaldi with the characteristic scalar passages alternating between the hands. South Germans Johann Jakob Froberger and Johann Pachelbel used to write this kind of music, too.
It starts with the opening cadence, emphasizing subdominant chords over the tonic pedal point which establishes the Eb major key. Later, the music moves to C minor (page 1-system 2-measure 3), Ab major (1-3-3), F minor (1-4-1), back to Ab major (1-4-2), Eb major (1-4-3), Bb major (1-5-1), C minor (1-5-3), G minor (1-6-2), C minor (1-6-3), and back to Eb major (1-7-4).
You may notice also a curious dominant pedal point in the C minor key (1-7-1 to 1-7-4) in a place where probably the preparation for the ending in Eb major (with the Bb in the bass) could be more expected.
An interesting feature of this prelude at the last line of that page is that only the chords are written, and you can add your own figuration in the arpeggio style.
When you play this prelude, you may experience some of the difficulties in these places:
1. (1-4-2) At the second half of the measure there is a tricky leap downward in the left hand part.
2. (1-6-1) At the second half of the measure only the bass should be played with the left hand. It's not very easy to figure it out right away. Therefore look ahead.
3. (1-6-2) At the beginning of this measure, your fingering for the left hand should be 3-5. Otherwise, there's no way to play tenor and bass together gracefully.
4. (1-7-1 to 1-7-3) If you choose to add arpeggio figures to the chordal outline, feel free to steal some figuration from 1-7-1, 1-4-1, or simply play arpeggio from the bottom note upwards (while holding the G in the bass).
The fugue starts with the chromatic subject. After the opening leap up a perfect fifth (or a perfect fourth in the answer), you may notice the chromatic half-steps filling in the interval of the perfect fourth (from Bb to F).
Here's the plan of this fugue:
1. (2-1-1) Eb major (tonic): bass
2. (2-1-3) Bb major (dominant): tenor
3. (2-2-2) Eb major (tonic): alto
4. (2-2-5) Bb major (dominant): soprano
5. (2-3-3) Eb major (tonic): alto
6. (2-4-1) Bb major (dominant): tenor
7. (2-5-1) Eb major (tonic): soprano
8. (2-6-1) Bb major (dominant): bass
9. (2-7-1) Eb major (tonic): tenor
10. (2-7-4) Bb major (dominant): alto
11. (3-1-1) Eb major (tonic): soprano
12. (3-1-4) Canonic stretto: tenor and bass
13. (3-1-5) Eb major: alto
14. (3-2-2) Canonic stretto: tenor and alto
15. (3-2-4) Canonic stretto: soprano and tenor
16. (3-2-5) Canonic stretto: bass and soprano
The fugue ends with the free improvisational episode which is similar to that of the Prelude (3-3-3). The key areas are Eb major (3-3-3), G minor (3-4-1), Eb major (3-5-2), Ab major (3-6-1), and back to Eb major (3-6-2).
Some of the more difficult places to play in this fugue are:
1. (2-4-1) Preparation of the left hand entrance in advance
2. (2-6-1 to 2-6-4) Thick chordal chromatic texture
3. (2-7-4) Syncopated tenor part
4. (3-2-2) Unexpected leap in the bass part
5. (3-2-4) Preparation of the subject entrance in the soprano part
6. (3-2-5) Preparation of the subject entrance in the bass part
7. (3-3-4) Modulation to G minor
8. (3-4-1) Scalar passage in the right hand part
9. (3-5-3) Notice the Db in the right hand part
10. (3-7-3) Rhythmically precise dotted eighth-note rest followed by the sixteenth-note in the alto part
I hope you will enjoy playing this well-crafted prelude and fugue. Here's the PDF score. If the four-part texture is too advanced for you, play hands separately in a very slow tempo using articulate legato touch (with small spaces between each note).