What's the most frequently found musical interval in tonal music?

Victoria Turcan: This photo was taken on Sunday, Aug 17, 2014 during the organ and cello recital ”My soul glorifies the Lord” at the Roman-Catholic Cathedral ”Divine Providence” from Chisinau, Republic of Moldova. Organ (Orgelbau - Fr. Fleiter) - Victoria Turcan, cello - John Koon from USA.

That would be sweet sounding thirds (and their inversions - sixths). They form the foundation of any musical composition created between ca. 1400-1900. Thirds can be the resolution after dissonant suspensions (4-3), they can be used in parallel motion upward and downward, in canon, or even in contrary motion between the parts of two hands.

Today we'll try to sight-read Prelude (p. 4-5) from the Prelude and Fugue in E minor, Op. 1, No. 1 (ca. 1905) by Moritz Brosig (1815-1887), little known late Romantic German composer and organist.

This Prelude consists of strings of major and minor thirds in parallel and contrary motion.

Here's how the Prelude is constructed in terms of this interval:

(1-1-2 to 1-1-3) Parallel thirds in the right hand part
(1-2-1 to 1-2-2) Parallel thirds in the right hand part
(1-2-3) Parallel tenths (a third plus an octave) between the left hand and the pedals
(1-3-1 to 1-3-2) Thirds in contrary motion between two hands
(1-4-3) Parallel thirds in the right hand part
(2-1-2) Left hand and pedals form canon in parallel tenths
(2-1-3) Parallel tenths between the hands
(2-2-1) Parallel tenths between the hands and the pedals
(2-2-3) Thirds and tenths in contrary motion between the hands and pedals
(2-3-1) Thirds and tenths in contrary motion between the hands and
pedals
(2-3-2 to 2-3-3) Parallel sixths in the right hand part
(2-4-1) Thirds and tenths in contrary motion between the hands and pedals
(2-4-2 to 2-4-3) Parallel tenths between the hands

Try to play this Prelude legato paying attention to the phrasing. For your convenience some fingering and pedaling are written in by the editor. Keep the fingers and the feet in contact with the keyboards and pedalboard whenever possible.