Her Royal Highness took the baton at the Hamburg Symphony Orchestra's new home, the Elbphilharmonie concert hall.
It was part of an event where 250 schoolchildren were introduced to music in front of the Duke and Duchess.
The Royal party are due back in the UK on Friday evening, after a five-day tour that began in Poland on Monday.
On the last day of the tour, the Duchess, who comes from a musical family and played the flute at school, took the musicians through the first notes of Beethoven's fifth symphony.
The royal couple then listened to a performance of a symphony especially adapted for young people, and then went on stage to learn more about the orchestra.
Earlier, Catherine and William walked around the stage accompanying six children trying out different instruments, including a violin, flute, timpani [kettle drums] and trombone.
Later the Duke of Cambridge gave Prince George and Princess Charlotte a guided tour of a helicopter at the Airbus factory in Hamburg.
Prince George tried on a pilot's helmet while Princess Charlotte played with buttons in the cockpit.
The Duke flew helicopters when he was an air ambulance pilot.
Antoine van Gent, head of flight testing at Airbus, said: "The Duke was very relaxed showing his children the professional aircraft he uses.
"George was excited, with the first helicopter he wanted to sit in the cockpit and then he wanted to sit in the next one, he already knew there was a difference between them."
Charlotte was less impressed after taking a tumble on the concrete after leaving the aircraft but Mr van Gent said she enjoyed playing in the pilot's seat.

The Ukulele Orchestra of Great Britain (UOGB) said their reputation could be tarnished by the German-based United Kingdom Ukulele Orchestra (UKUO).
The UOGB had sought a High Court injunction against the rival group of British players ahead of the UKUO's upcoming UK tour.
But the judge ruled in favour of the UKUO, saying it was not in competition.
Judge Richard Hacon agreed that, as the group had been performing in Germany for some years, the UOGB should have acted sooner.
Both orchestras perform their take on contemporary pop songs.
The UOGB, whose members dress like a traditional orchestra and sing and tell jokes on stage, have been performing for more than 25 years, released records and have appeared on television.
The British group took action ahead of the UKUO's first UK tour, which begins on 15 October in Lincoln.
"We have issued proceedings against a German-based musical group for registered trademark infringement. However the court didn't grant the injunction," UOGB founder George Hinchliffe told the BBC at the London court.
He added: "It's really not a policy of ours to comment upon litigation while it's still going through the courts. And we're a bit busy at the moment as we're just about to start a tour of China."
The court heard the UKUO performed in English and had a "certain English humour" which was aimed at the continental market and Germany in particular.
"We are very pleased with the outcome," said Peter Moss, UKUO musical director.
"Our view has always been that we never, ever wanted to have competition with the other side. We wish them well. We hope people will now come to see us play."
The UOGB said they was considering further legal action to protect their "name and reputation".
The Duchess of Cambridge tried her hand at conducting a prestigious symphony orchestra on the final day of the royal tour of Germany.
[NEXT_CONCEPT]
A British ukulele group has lost its trademark infringement battle against a rival band over its name.