If all goes as expected, the position will go to either Daniel Barenboim, who already holds two of the most lucrative conducting jobs, at the Berlin State Opera and the Chicago Symphony, or Sir Simon Rattle, who turned the City of Birmingham Symphony Orchestra into a world class ensemble before going freelance two years ago.
But it is not just about the choice between two men. Musical insiders say that the decision will reflect whether the orchestra has chosen to look backwards to a more traditional era or forwards to the new millennium.
"Barenboim is considered to be the traditional choice who likes to play the romantic and classical composers, like Mozart, Brahms and Bruckner, but the younger players are more in favour of Rattle who they see as more radical and full of new ideas," said one industry insider.
"Basically if you want to look backwards you would go for Barenboim but if you want to move into the 21st century then Rattle is the one to go for."
The post of chief conductor is usually for life but Claudio Abbado, the present incumbent, is standing down after only nine years.
As one insider put it, Abbado, "has decided that he doesn't want to deal with it all any more. Those musicians have, one could say, a very good sense of their own worth."
The BPO is unique among orchestras in that its musicians decide who will lead them. Later today all 112 full-time members will cast their final vote for only the seventh senior conductor in 132 years.
The musicians will vote in a secret ballot at a secret location and are bound by a code of confidentiality.
The orchestra's official spokeswoman said reports of a head to head between Rattle and Barenboim were wrong.
"It is not between those two," she said. "That is all speculation. It's possible that they could decide on someone completely different."
But a BPO insider admitted that everyone had been told to keep quiet before the result was announced. "No one is saying anything," he said. "It is always a tightly kept secret."
One recording industry executive said that the BPO should go for Rattle.
"Rattle could have his pick of any orchestra in the world. Berlin should vote for Rattle because whatever he does is exciting and it is a new challenge. He doesn't take the safe option and the breadth of his repertoire is just matchless."
Keith Clarke, of Classical Music Magazine, said that both conductors were equally talented but Rattle would be the better choice. "Barenboim is staid and traditional and I would always go with the revolutionary but in the end it will depend on how many musicians feel that way and that it why it is so hard to predict who will be the winner."
The candidates themselves have refused to comment publicly on the matter but Barenboim has been lobbying fiercely behind the scenes. Rattle has preferred to put his case through his music and has received ecstatic reviews from the German press.
"A concert of such mould-breaking quality that one can only have pity for those Mahler lovers who could not hear it," raved the Frankfurter Allgemeine Zeitung.
In his only comment before taking himself off on safari with his sons until after the voting, Rattle said simply that the orchestra needed to decide whether it wanted to be "an artistic institution or a media enterprise".
This was viewed as a thinly veiled criticism of those who believe that Barenboim's plans for the orchestra to make world tours and recording deals would be better for business.
Rattle's supporters are believed to think privately that the vote for their man is in the bag but the BPO is notoriously insular and it is impossible to predict the outcome.
After all, nine years ago, when a vote was last held, they were thought to be voting between Lorin Maazel and James Levine. Maazel was so confident of his appointment he organised a celebratory press conference in advance. The orchestra chose Abbado.
Widower of the cellist Jacqueline du Pre, who died in 1987; married in 1988 a Russian pianist, Elena Baschkirova. They have two children.
Past form: Child prodigy who performed with the BPO as a pianist. Currently the conductor at the Berlin State Opera and the Chicago Symphony. Champion of the traditional.
What the critics said: "A jack-of-all musical trades, head of Berlin's Linden-Opera, Chicago Symphony general, pianist, tango-player, universal genius with little time for rehearsal and too few moments of musical glory."
What the supporters said: "When he's in town, it's great. But when he isn't, the energy flags. If he were to go, it would be a catastrophe."
Sir Simon Rattle
Father of two, remarried to script editor Candice Allen. Outspoken critic of Labour's arts funding, which he says may induce him to leave Britain.
Past form: A child prodigy, he changed the City Of Birmingham Symphony Orchestra into a world-class ensemble during his 17 years as the conductor. Has been freelance for two years but any orchestra in the world would love to have him. If he does not get the BPO, its great rival, the Vienna Philharmonic, will create an honorary position for him.
What the critics said: "A foreigner with no sympathy for our traditions."
What the supporters said: "The BPO must choose this superman. What else do they want?"Reuse content