A private investigator has been hired to patrol public areas and report people playing music without paying licence fees.

Auckland designer Alex Webster was stunned to find he had been secretly filmed in his company's showroom.

The investigator said in his report to law firm James & Wells that he called at the office and showroom at 12.06pm on May 22.

"Alex Webster had pop star Beyonce singing Halo and indie band MGMT's Electric Feel on the MP3 player," the report said.

"The music was played very softly and it was necessary to listen to the recording carefully at times to hear the music playing in the background."

The law firm was working for the record industry copyright collection body Phonographic Performances New Zealand (PPNZ).

Mr Webster said PPNZ had gone to a lot of effort to recover the $155-a-year fee for playing music.

Music specialist Chris Hocquard, of Dominion Law, said music companies were under pressure to recover money to counter falling record sales revenue.

Last month, the Cafe Paradiso and another Tauranga eatery complained about a demand that they pay a fee for CDs played in the background.

Mr Webster said he believed the MP3 player played in his open-plan office and showroom in Freemans Bay did not meet the definition of a public performance requiring a licence.

But he had given up trying to avoid a copyright fee.

It had become stressful and costly to challenge a PPNZ writ.

The collections agency said the money went to record companies and artists.

"PPNZ works hard to ensure that the rights of copyright holders are maintained," a spokesman said.

"It takes this role seriously and believes its processes to be fair and justified."

PPNZ public relations adviser Quentin Reade said Mr Webster had been given plenty of time to pay the $155 fee. PPNZ would be going ahead with legal action in the Auckland District Court despite Mr Webster's saying he would pay.

Mr Webster said he would complain to the Law Society about James & Wells' approach.

The firm emailed asking him to say if he was playing music.

"I thought it was spam and ignored them, but then received an officious-looking letter from James & Wells 'requiring' a response within 7 days."

He replied, saying he did not have to tell the firm anything and it was "fishing" for information.

James & Wells did not return calls from the Weekend Herald.

The $155-a-year fee covers music in retail space of less than 1500sq m.

Phone music played while callers are on hold costs $83 for up to 20 lines and $4.15 a line after that.

Nightclubs pay $415 to $620 a year to play music and restaurants, cafes and bars pay $155 to $620.

The most expensive licence is for urban sports venues. Fees range from $320 for a venue in a town with up to 10,000 people to $2600 for one in a town with more than 50,000 people.