Cornelius Ryan's "The Last Battle" goes into some details about the Berlin Philharmonic, and Albert Speer's involvement and efforts to evacuate them prior to the Soviet occupation of the city.
All 3 of his books are well worth the read, as they were written in the 50's-70's and include plenty of interviews with actual participants of WWII.
Is this, "Hitler governed by executive decree, a method that has suddenly come into vogue again." referring to the Executive Orders issued by President Trump and Obama as of late? Well if so, it certainly is not even close to the executive orders issued by Hitler. U.S. presidential executive orders are still subject to judiciary review and can be struck down; and then there is the power of congress to pass laws that can override them (although they could be vetoed by the President).
All 3 of his books are well worth the read, as they were written in the 50's-70's and include plenty of interviews with actual participants of WWII.