On his mammoth 1974 tour to promote the album Diamond Dogs, David Bowie began the first leg with the usual Glam theatrics he was dealing in at the time (an over-the-top re-creation of 'Hunger City', the setting of the Diamond Dogs album; a cherry-picker he sat on which went over the crowd; singing into a telephone etc.) However, by the time the second leg kicked off in LA, Bowie had acted on his nascent obsession with Philadelphia soul music by transforming the show into more of a soul revue, stripping away any pretence and often featuring a stark white backdrop in front of which he almost carried out a one man show.
Changing the whole set and feel of a tour halfway through is pretty radical and something promoters of acts as big as Bowie (if there are any) simply wouldn't stand for today. The fact that many American concert-goers were expecting one thing but were given something completely different demonstrates Bowie's relentless imperative to act upon whatever took his fancy at the time. Also he managed to complete the tour on a diet of red peppers, milk and, most importantly, cocaine. What an engine.