Novak Djokovic takes Serbian crowd off guard at a gig, not just by being there, but by playing jazz on a sax!

Novak Djokovic got the chance to try out his saxophone skills in front of a concert crowd in Belgrade on Tuesday, October 24.

The World No. 1 was spending time with his family, attending a concert by Croatian cellist Stjepan Hauser, known professionally as HAUSER. The musician has released six albums as part of the duo 2Cellos, consisting of classical and film music, as well as cello covers of well-known pop and rock songs.

Djokovic has had a dominant season this year, having won three out of four Grand Slams and equaling Margaret Court's record of 24 major titles in the process.

Therefore, after a busy summer schedule, the tennis star announced that he would be skipping several tournaments in the fall, planning to return at the Paris Masters which begins on October 30th.

During the concert in the Serbian capital Belgrade, HAUSER invited Djokovic onto the stage, where he entertained the crowd by showing off some saxophone skills.

This is just one of the many non-tennis activities that Djokovic has been enjoying since his victory at the US Open last month. The 36-year-old returned to Belgrade from New York shortly after his win to celebrate Serbia's silver-medal finish at the FIBA Basketball World Cup.

He then competed in the Celebrity All-Star Ryder Cup alongside the likes of Gareth Bale and Carlos Sainz, which he called a "once-in-a-lifetime experience."

At the end of October, Djokovic will return to the ATP Tour for a busy few weeks, including the Paris Masters, the Davis Cup quarter-finals, and the Nitto ATP Finals.