Cyprus, Israel, France and Norway are among those predicted to do well but unlike last year -- when SalvadorSobral took the Eurovision crown with a jazzy-style ballad -- there is no out and out frontrunner.
The event in Lisbon comes as cash-strapped public broadcaster RTP said it was planning a more "theatrical" contest that makes less use of video projections and new technologies, following in the footsteps of Sobral's performance at the festival in Kiev last year.
Sobral, 28, who said after his win that "music is not fireworks, music is feeling", turned down the lights and simply swayed to the music as he performed "Amar pelos dois" ("Love for Two"), a song penned by his sister.
"We want our project to be as simple and elegant as Salvador Sobral's performance in Kiev," said Eurovision executive producer Joao Nuno Nogueira last month as he discussed RTP's plans for the contest, often billed as the biggest non-sporting television event in the world.
He would not say exactly how much Portugal had spent on staging Eurovision, only that it would be less than 25 million euros ($30 million dollars) which would make it the lowest budget contest in a decade.
'Different feel'
The president of Britain's main association of Eurovision fans, Alasdair Rendall, welcomed the changes, predicting it would give a "different feel" to the contest, started in the 1950s with the aim of uniting Europe after World War II.
"I think it will make it more of a live music show, it was in danger of becoming too much of a pure TV show," he told AFP.
"Some of the graphics and LED screens have been taking away from the performance element of it," added Rendall, who has attended 10 other Eurovision finals.
Sobral's victory was the first time Portugal had won Eurovision since it entered the contest in 1964 -- and the first time a song sung entirely in a language other than English had won since 2007.
His success appears to have inspired more countries to field candidates performing in their mother tongue.
Of the 43 acts taking part this year, 13 are sung entirely in a language other than English, up four from last year.
Repeat winner?
Among those tipped to win the outlandish annual extravaganza is Norway's Alexander Rybak, who won Eurovision in 2009. If he does, it would be only the second time in Eurovision history that the same singer has won twice, after Ireland's Johnny Logan in the 1980s.
After getting some chiding for picking three men to host last year's competition, contest organisers this year enlisted four Portuguese women to host the final, including Daniela Ruah, who stars in the hit US TV crime drama "NCIS: Los Angeles".
Sobral will perform on Saturday for the first time since he underwent a heart transplant in December.
Lisbon's riverside Praca do Commercio has been converted into a buzzing "Eurovision Village", complete with bars and food trucks, which will broadcast the contest being held at the Altice Arena, located on the outskirts of the city.
For those without tickets, the competition will be broadcast on a giant outdoor screen.
Viewers and professional juries in all 43 participating countries will pick the winner, with the televoting and juries each representing 50 percent of the outcome.
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