But the DJ priest is a sensation in Portugal, greeted like a rock star wherever he goes.
"I feel I'm a better priest thanks to electronic music," said the 50-year-old, whose popularity exploded after he played a set to nearly 1.5 million young people and Pope Francis last year at the closing mass of World Youth Day in Lisbon.
Once a Catholic chaplain to Portuguese troops in Afghanistan, he realised there that his passion for music could help him get the church's message across.
So he went to DJ school.
"It allowed me to take up the challenge that the church gives us not to turn in on ourselves but rather reach out to others," he told AFP.
Known simply as "Father Guilherme" in Portugal, the shaven-headed cleric regularly swaps the altar for a DJ's mixing table at festivals and clubs across Europe.
Techno popes
He juggles his burgeoning music career with his duties as a parish priest in Laundos in northern Portugal, where he often slips on his chasuble to say mass over jeans and trainers.
Equally popular with his parishioners, Father Guilherme sees no contradiction between getting people dancing and preaching the Christian good news.
He said getting the word of Christ out there "rhymes with the beauty and harmonies of electronic music".
"The joy of the gospel is a message of hope and faith but also of tolerance, harmony and peace," added the priest, who has 900,000 followers on Instagram.
Playing to hundreds of young people in the university city of Coimbra this month, he mixed bits of techno with excerpts of homilies by Pope Francis and the late John Paul II.
"He has managed to bring together two seemingly opposing worlds," said Filipe Barroso, a 32-year-old electro fan. "I think what he does is really great."
