Mike Gleaden discovered the stolen items after moving furniture with his brother ahead of the empty property being sold.
He quickly rang the police after discovering a number of sentimental items belonging to his late parents had been taken.
Two silver watches, a silver cigarette case, silver napkin rings and a silver christening mug were all stolen, along with the musical instruments.
The 61-year-old lost his mum earlier this year aged 88- she was a week shy of her 89th birthday. He said: "I'm absolutely devastated, to tell you the truth.
"My poor mum died in May after contracting the coronavirus in Doncaster Royal infirmary while recuperating from a stroke. We've obviously had a really difficult year and this just adds to the misery.
"These items are hugely sentimental to my family. All the items belonged to my parents, being handed down from their parents.
"The flute and piccolo originally belonged to my grandfather, who was a bandsman and stretcher-bearer with the Sherwood Foresters in the First World War and took the instruments with him to France in the trenches.
"They are at least 100 years old and could be quite valuable. They were left to my father as a five-year-old when my grandfather died as an indirect result of being gassed.
"Dad was musical too, having played the church organ at Babworth for many years.
"The cigarette case came back from China from my other grandfather, who was out there with the British Army, so again could be of decent value.
"I'd imagine it they’d be quite difficult to shift, but we keep looking online ourselves to see if they pop up for sale and have contacted all the leading antique musical instrument dealers giving them the details including the unique serial numbers.
"I was shocked when we made the discovery, not least because my brother and I had been in the house for around an hour moving furniture and not noticed anything disturbed.
"It wasn't until we were in the garden, we spotted some keys on the floor.
"If anyone comes across them, please let us know."
The incident happened between July 22-24 when the house in Ordsall Road, Retford, was broken into and several items were taken.
The Flute by Rudal Carte & Co has the serial number 7516 inscribed on it, meanwhile the piccolo by Rudal Carte & Co had the serial number 7122 printed on.
Police Constable Poppy Macky, of Nottinghamshire Police, is leading the investigation. She said: "We are keen to speak to anyone who saw anything suspicious around the time.
"The instruments are quite distinctive and have serial numbers engraved on them.
"Meanwhile, the silver tankard was also inscribed 'Simon James 12th February 1964'.
"We are appealing to anyone who may have come across the items at a car boot sale or on an online auction site. If you recognise the items, we'd love to hear from you.
"The Gleaden family have gone through a horrendous 2020 so far, so we are hoping we can get the sentimental items returned to them.
"Please call 101, quoting incident number 374 of 25 July 2020 if you think you can help."