And, No Tony, I'm not kidding - it's called ad liibbing: Short for ad libitum. A term used in jazz music as a slang for an improvised solo, or a solo performed without written notation, but where the performer improvises a melody based around the melodic and harmonic structure of the original melody.
Gary

Which has little or nothing to do with what we're talking about here. There is a slight difference between a melody and a chord change. In general, one can be improvised freely; the other, with a great deal of caution (and musical knowledge).
As for the post being primarily about STYLES, (IMO) a style is best demonstrated when the listener is not distracted by errant chords. JMO.
chas (JMO MEANS JMO)