This paper closely examines the performance practice regarding articulation of the preludes from Bach’s Well-Tempered Clavier Book I. Recordings by five pianists are studied: Vladimir Feltsman, Glenn Gould, Angela Hewitt, Andras Schiff, and Rosalyn Tureck. The recordings reveal certain recurring articulation patterns which are categorized into six articulation techniques: short slurs, long slurs, detached upbeat, accented downbeats, changing articulation, and rolled chords. The author has divided the preludes into four groups: preludes with continuous running figuration, lyrical preludes, lyrical preludes with distinct melody and accompaniment, and preludes with non-lyrical themes. Analysis reveals that for each group of preludes, there are a set of principles that these pianists follow. Overall, for non-lyrical preludes, the running sixteenth notes are played legato, staccato, or a short slur followed by staccato. The slower moving quarter and eighth notes stay mostly detached or staccato. For lyrical preludes, the melody remains largely legato. Articulation techniques are used more extensively in non-lyrical preludes than lyrical ones, and more often in the slower moving eighth notes than running figuration. Articulation techniques are often used as means of embellishment. They enhance the individual character of each piece and generate Baroque attributes. Despite the principles observed in the recordings, many isolated performances are found which do not conform to any of them, suggesting that there is no authoritative rule when articulating Bach’s works on piano.