(CNN) -- Russia and Ukraine will face off again Saturday. But this time it's not the geopolitical arena where the action takes place -- but the glitzy stage of the Eurovision Song Contest.
Both countries have made it through the semi-finals to compete in the grand final in Copenhagen, Denmark.
The usual artistic rivalry has been given an added piquancy by the tensions between Russia and Ukraine. Moscow annexed Ukraine's Crimea region in March and eastern Ukraine is currently roiled by pro-Russian separatist protests.
The organizers describe Eurovision -- widely loved for its combination of over-the-top costumes, kitsch pop songs and sometimes questionable talent -- as a non-political event meant to unite Europe through song.
But in reality, politics inevitably colors both the voting and the performances.
This was demonstrated to an unusual degree on Tuesday, when Russia's entrants -- 17-year-old twins Anastasia and Maria Tolmachevy -- were booed by the audience during their semi-final performance.
William Lee Adams, a Eurovision expert and the editor-in-chief of Wiwibloggs.com, the popular Eurovision website, told CNN that the contest is about national identity as well as music.
"Months of frustration over Russia's illegal annexation of Crimea and Putin's anti-LGBT laws have left Europeans angry," Adams said.
"The booing was a release, a statement of solidarity with Ukraine and Russia's sexual minorities."
It doesn't help that Russia's love song features lyrics that some see as hinting at a border incursion. It goes, "...living on the edge, closer to the crime, cross the line, one step at a time ... maybe there's a day you'll be mine."
Ukrainian singer Mariya Yaremchuk, who is performing a song titled "Tick-Tock," said Tuesday that she was proud to be representing her country.
"Actually, my main position is that I'm proud that I'm Ukrainian and everything I do here is for the Ukrainian people," the 21-year-old said.
"I'm not standing alone on the stage, there are 46 million Ukrainians behind me on the stage."
Yaremchuk will be the first to perform on Saturday night, while Russia's Tolmachevy Sisters will be 15th out of 26 finalists to take the stage.
After the singing comes the voting.
Former Soviet nations have tended to award their votes to each other. Whether the crisis in Ukraine changes that equation remains to be seen.
The countries involved in the contest award a set of points from one to eight, then 10 and finally 12 for their favorite songs. They can't vote for themselves and they must announce the score in both English and French.
Television viewers can cast votes in their respective countries through telephone hotlines, which count for half the final tally. The remainder of the vote is cast by national expert juries.
The country with the highest points total wins -- and has the rather expensive honor of hosting the following year's event.
In 2013, more than 180 million viewers in 45 countries tuned in to the action.
CNN's Tara Kelly and Jim Stenman contributed to this report.