The “central tone” of your examples is either the root tone of the key tonic or the dominant:
For example, in a piece I am playing, the melody is: F C G C Ab C Bb C.
This is the scale of f-minor (F,G,Ab,Bb,C) and it’s always turning to the 5th as changing tone, very usual in Baroque era, but also known in Classic music as Alberti Basses.
Eb C F C F# C G C Bb C
This is a typical Blues pattern:
The root of the tonic of your Blues Scale can be considered as pedal tone like another answer says.
You may also know Odyssea Beneziana by Rondo Veneziano
Both features occurred already in the modes of Plain chant:
The recitation tone, the repercussion note, the repercussa, the tenor, the tuba, or even the psalmodization sound is an important structural tone within the church modes.
In addition to the basic tone, the finalis, in the medieval tones systems there is always another tone, the recitative tone, a role in the melodic progression. This sound is usually achieved at an early stage within a melodic section, and it is played more often than other tones. In the psalm tones, the recitative tone is the tone on which much of the psalm text is recited.