But the album was greyed out and unavailable to play in Australia. It was one of those mildly annoying things that makes you think about how things work.

The number of Australians using streaming services to listen to music is growing, with more than 80 per cent of Australian musicians' recorded revenue now coming from streaming.

Using any of the paid services in Australia — Spotify, Apple Music, Amazon Music Unlimited, YouTube Music, Tidal, just to name a few — will give you access to an enormous library of music from all genres, locations and eras.

But occasionally, your search for an old favourite or a popular song will come up empty. Sometimes songs will suddenly disappear from the service. Other times the song will only be available on a competing service.

So what determines which songs make it onto streaming services in Australia?

How music makes its way online

It comes down to the choices artists make when they want to get their music out to the world.

Streaming services don't tend to deal with artists directly. So there are two major ways of getting your music onto a streaming platform: by agreeing to distribute your music with either record companies or digital aggregators.

Record companies (or record labels) have long been the dominant form of mainstream music distribution. The model is, generally, that artists sign to a label who assist in the production, promotion and distribution of music.

Since the inception of music streaming, distribution has expanded to include delivering music digitally via streaming platforms.

But some major artists with record deals haven't always given permission for their music to be streamed. Taylor Swift notably pulled her music off streaming services in 2014 over how much artists were paid, joining other holdouts like the Beatles, Prince and Tool. Swift, like the others, eventually relented and released her music to the streaming services in 2017.

Other popular artists like Aaliyah or De La Soul still haven't licensed their back catalogues to the streaming services.

Then there's the music that was released before streaming was invented. Most record companies have made their artists' back catalogues available for streaming — although there are exceptions like The Tenant's Australian pub rock classic You Shit Me To Tears — but independent artists would have to go through a digital aggregator to make it available.

Going independent

The new kids on the block are the digital aggregators. These companies offer a range of services, but their main gig is getting music on streaming services after the artist has made it.

Andy Irvine is the CEO of an Australian digital aggregator, GYROstream. He said while platforms, such as Spotify, have trialled allowing artists to upload their music directly, the streaming services prefer the simplicity of dealing with distributors.

"Streaming companies don't want to deal with over a million artists, they prefer to deal with a few companies. Major labels have their own deals with streaming services.

Then we have our own deals with many services around the world," he said.

Mr Irvine said that as improvements in technology have made it cheaper and easier to produce and distribute music, artists are eschewing traditional label deals and staying independent. This means there's a demand for the digital aggregators.

Chris Endrey is an independent Australian artist who's used digital aggregators to get his music onto music streaming services.

Even though streaming revenue is notoriously low, Mr Endrey thinks there's a value in making music easily accessible.

"Nobody buys content any more," Mr Endrey said.

"I still release music on Bandcamp where people can purchase it outright, and I raise money through Patreon. But I direct people first to Spotify, Apple Music, or wherever, because I make stuff because I want people to listen to it."

Mr Endrey said the barrier to entry to getting music on a streaming service is surprisingly low. All it takes, he said, is meeting some minimum requirements for your music and song artworks, a short wait and a small amount of money.

"You are seven days and fifty bucks away from getting your song from GarageBand onto Spotify," he said.

Music licensing can get complicated

That's how online music distribution can work. But agreements between rights holders and streaming services are often a lot more complicated, and this can result in music being held off streaming platforms.

While some musicians will choose to grant a global license to a distributor, others choose to instead license their music to multiple distributors — usually broken down by country or region — in something that's known as a "carve out".

Every time there's a carve out, each distributor has to come to an individual agreement with the company to get the music on the streaming platform.

If they don't, people won't be able to listen to that music even though it's available to people in other countries.

Sarah Hamilton is the regional director of Ditto Music, an international digital aggregator.

She said that most emerging artists will sign global deals, but other established artists may want to work with certain domestic distributors who know their markets well.

"Some people will carve it up, but it gets really tedious for management to have to deal with different time zones and make sure everything is online," she said.

Sometimes differences in countries' copyright laws will affect licensing as well.

Unlike in Australia, artists have to pre-emptively purchase a license in the US to record a cover of another artist's song, Ms Hamilton said. Alternatively, the artist may choose just not to make their version of a song available on US streaming services.

Streaming is relevance

Dr Charles Fairchild, associate professor of popular music at the University of Sydney, said the accessibility that comes with streaming isn't just an important source of income for artists — it's also a big factor in their cultural relevance.

"The music industry used to be quite protective about licensing their music, but now the answer is always to yes," he said. "When it comes to streaming — which is like ubiquity squared or cubed — it's about being able to access this piece of music whenever I want."

"From my view, it's hard to understate the importance of being on streaming platforms," he said.