Another crucial point is the artists  share of the cake, as some of them have complained over losing money because of music streaming.

In 2014, Taylor Swift, a UMG superstar, removed her albums from Spotify, saying it hurt her music sales.

"I think there should be an inherent value placed on art. I didn t see that happening, perception-wise, when I put my music on Spotify," Swift told Time magazine in 2014.

UMG, which controls labels like EMI, Capitol, Virgin, Polydor or Geffen, have signed record deals with such mega stars as Adele, Jay-Z, Lady Gaga, Massive Attack, Enrique Iglesias, Lana Del Rey and U2.

On this sensitive subject, Spotify s agreement with Universal remains unclear.

"Under the agreement, the companies will advance their partnership to ensure that streaming realises its full transformational potential for artists, labels and fans," the companies said in the statement.

Spotify, which is available in 60 markets, exceeded 50 million paying subscribers in early March.

The company is growing and consolidating its position as the world s number one compared with competitors like Apple Music or Deezer.

It did not mention progress in negotiations with the two other majors companies, Sony and Warner.

"The fact that (Spotify) can become profitable will allow them to go very quickly on the stock market," Verney said.

"There s no reason why it should take time now."