More than 1,000 voted to "fight hard" to save the Bridgend engine plant, says their union.Read more
Ford and Volkswagen are close to reaching an agreement to cooperate on the development of autonomous cars.
In March, the two firms signed a deal to build a pickup truck together and, now, it looks like they may also partner to design self-driving cars.
VW's chief executive, Herbert Diess, said talks between the two motor giants are "going well and are nearly complete".
Ford was a little more cautious. It said talks were ongoing, adding that it would share more details once the details are agreed.
"Discussions have been productive across a number of areas," a spokeswoman said.
The choir sang the Welsh national anthem outside Ford's UK headquarters in Essex.
It was announced on Thursday that Ford's engine plant in Bridgend will close in 2020.
BBC Radio 4
BBC Radio 4's Today Programme has been looking at the announcement by Ford yesterday that it will close its Bridgend plant, at the cost of 1,700 jobs.
The company put the decision down to "changing customer demand and cost".
However, Chris Jones, co-founder and chief analyst at Canalys, described Brexit as a "dark cloud" that lingers over car manufacturers in the UK - but there are also broader factors at play.
"Car sales are down - they're down in Europe they're down in the US, they're down in China - and they [car makers] have to adapt to that.
"They manufacture cars around the world and they have to decide what to build, where to build it and how many to build.
"So they have to make these tough decisions about what the demand for their vehicles, for there engines, is and will be over then next few years."