* Vivendi shares rise on news
* Investors growing impatient with sale
* Valuation boosted by streaming services (Adds details)
By Gwénaëlle Barzic
PARIS, July 24 (Reuters) - French media group Vivendi is set to appoint several investment banks on Thursday for the sale of up to 50% of Universal Music Group, its most-prized asset, said a source close to the matter.
It has been a year since the Paris-based company said it would sell part of the division, unnerving investors and leaving equity analysts scrambling on the asset's valuation, with estimates ranging from 17 billion euros ($19 billion) for Redburn to 44 billion euros for JP Morgan.
The group, controlled by billionaire Vincent Bollore, is seeking to cash in on the growing public thirst for subscription and ad-based music streaming services, which have propelled Universal's profits over the last four years.
Vivendi shares gained on Tuesday's news and was up 1.2% in late trading, outperforming a 0.1% fall on France's benchmark CAC-40 index.
The group, which reports first-half earnings on Thursday, declined to comment.
After a 15-year downturn, the music industry has rebounded, with global recorded music revenues increasing by 9.7% in 2018 - the fourth straight year of growth - to $19.1 billion, according to the record industry trade group IFPI.
Universal is the world's biggest music label ahead of Sony Music Entertainment and Warner Music, and is home to artists like Taylor Swift, Drake, Kendrick Lamar and Lady Gaga.
When reporting its annual earnings in February, Vivendi pledged to provide a list of investment banks "within a few weeks".
Prior to this, it had said it planned to select between six and seven financial advisers out of a short-list of 15 banks. But so far, Vivendi has only mandated accounting firm PwC for a "vendor due diligence" that was presented to the group's supervisory board in May.
Investors' concerns on the sale process have recently been fuelled by a New York Times story about a 2008 blaze that destroyed original recordings, or so-called "masters", archived by Universal.
In a letter sent to staff and seen by Reuters, Universal's boss Lucian Grainge said in June that he would address any worries expressed by artists, pledging to be transparent about the extent of the damages.
"We owe our artists transparency. We owe them answers. I will ensure that the senior management of this company, starting with me, owns this," he wrote then.
Some analysts have also pointed to the potential difficulty in finding a partner willing to share power with Bollore.
($1 = 0.8969 euros)
Reporting by Gwenaelle Barzic; Writing by Mathieu Rosemain; Editing by Jean-Michel Belot/Sudip Kar-Gupta and Emelia Sithole-Matarise