In recent years the music industry has been feeling optimistic again, two decades after Napster cost it millions in lost revenue.

The strongest growth in 20 years occurred in 2018, a signal that the take-up by music fans of paid streaming services like Spotify and Apple Music was making digital piracy — the illegal downloading that made Napster notorious — less attractive.

But piracy has not disappeared. It has just changed form.

"Downloading used to be the big issue," said Vanessa Hutley, the general manager of Music Rights Australia.

"But what we are finding is that these illegal stream-ripping sites are the growing trend."

Stream-rippers 'rip off Australians'

Stream-ripping is the process of taking a streaming link — for example, a YouTube URL — and pasting it into a tool, usually a free website, that then converts the audio into a downloadable file.

The issue came to the Federal Court on Tuesday, as major Australian record labels join royalty agency APRA in a push to make sites that offer this service, including 2conv.com, Convert2mp3.net and Flto.com, inaccessible in Australia.

APRA and the labels say those websites are "flagrant" in their facilitation of copyright infringement, and that it is their primary reason for existing.

"There are many avenues for consumers to get the music they love at a range of price points from licensed streaming services and licensed digital services," said Ms Hutley, whose organisation is managing the case.

"These sites do nothing but rip off the creativity of Australian artists and Australian labels."

Ms Hutley could not put a dollar figure on how much lost revenue these sites cost Australian musicians, but in the US, court documents revealed the sites were available in 23 languages and that Fltvo.biz, which carries advertising, received 263 million visits in the 12 months to 2018.

"I think it all leads back to the value that is placed on music, and a little bit of that has been lost over the years" as music has become ubiquitous online, said Kristy Lee Peters, the producer and DJ better known as KLP.

She said blocking stream-ripping sites was helpful, but that the "bigger picture" was that fans needed to see the worth of a musical creation.

"If you understand that, you just don't want to use those sites ... you will still choose to actually pay for a subscription on a streaming platform, or pay for a download of something."

US attempt to go after sites failed

The websites have been the subject of legal action in countries around the world, and last month, the music industry suffered a setback in its battle against them.

The Recording Industry Association of America (RIAA), along with some of the biggest record labels in the world, had been suing a Russian developer named Tofig Kurbanov, who owns and operates at least two of the stream-ripping sites, Fltvo.biz and 2conv.com.

Kristy Lee Peters, the producer and DJ better known as KLP, says the court action is helpful, but education is needed. ( Supplied )

The music industry claimed Mr Kurbanov's sites were providing a service — to 31 million Americans in the past 12 months, it said — that constituted a vehicle to commit copyright infringement.

Last week Mr Kurbanov, who had held out when other foreign-owned stream-ripping sites had folded under the pressure of lawsuits, successfully had the case dismissed.

A judge ruled that despite the site having customers in the US and working with US domain registration and hosting firms, it was a foreign entity, owned and operated by a foreigner with no ties to the US, that could not be sued in an American court.

Mr Kurbanov's lawyer, Val Gurvits, said his client was not available for interview.

APRA, in its pursuit of Mr Kurbanov and others, is using a no-fault remedy available under Australian copyright law to get around this specific problem.

"It allows us to file cases naming carriage service providers, the telecommunications groups like Telstra and TPG and Optus, but they are not at fault," Ms Hutley said. "They really are just a mechanism to block access to these illegal sites."

It is the same method the industry used two years ago when it went after Kickass Torrents, a website that let users download music files illegally.

Could the link's owners do anything to stop this?

YouTube is increasingly becoming a platform for listening to and discovering music, particularly among young people.

Video streaming accounts for more than half of on-demand music streaming time, according to a report last year from IFPI, a global music rights organisation.

YouTube is likely the kind of place where the links used on stream-ripping sites eventuate, given the popularity of YouTube-mp3.org, which was shut down in 2017.

Could that platform, owned by Google, do anything to stop the practice?

YouTube would not make anyone available for interview, but in a statement a spokesperson said YouTube's terms of service prohibited the downloading or copying of videos without the copyright holder's consent.

"Once notified of an infringing tool, or service that allows the downloading of a YouTube video without permission from the content owner, we take appropriate action," the spokesperson said.