Gibb Sahib wrote: If so, why did Neil sing a different tune in 1969?

For what it's worth, John Roberts, who had better musical sense than I do, suggested to me (in a private communication) that Tommy's tune is basically Colquhoun's done in major (or that Colquhoun's is Tommy's converted to Aeolian, expressed as Dorian in Colquhoun's guitar arrangement). Just another little complication.

John Archer's work did reveal one very important point: That Colquhoun's tune preceded "The Lightning Tree."