The bariolage technique is a contrapuntally rudimentary yet much used technique of reducing two upper voices of a setting into one voice by successively alternating a note of one voice with a note of the other voice. Bariolage, a typical violin technique that works very well on the keyboard as well, is thus a specific form of compound line.
Here you see a four-part C major chord in first position:
We then omit the fifth of the chord:
We are now ready to transform the sixth in the right hand into a bariolage setting. To do so on the keyboard, one plays alternately its lower and upper note:
For more information on the bariolage technique, see my YouTube video: