'freelance interpreter' is correct and usable in written English.
You could use it when you are referring to an interpreter who works without having a contract with a specific company or organization. For example, "We are looking for a freelance interpreter to work on a short-term project."
Besides being a musician, Mr. Granafei worked as a "freelance interpreter" to make ends meet.
Kenji is the curiously passive freelance interpreter who is unable to translate the horror in which he is complicit.
The American military has described Mr. Kandahari as a freelance interpreter who had volunteered to help the American Special Forces, who allowed him to live at their base in exchange.
She also works as a freelance interpreter and a translator and teaches one class a year at Otis.
His mother is a freelance translator and interpreter in Washington.
His mother is a cataloger at the Rockefeller Library at Brown and a freelance translator and interpreter.
Her mother is also a freelance language interpreter.
Alisher Khamidov Elina Kalnina's job description is certainly unusual: freelance heritage interpreter.
Mr Somers was born in Britain but spent most of his life living in the US before working for almost two years in Yemen as a freelance photojournalist, interpreter and copy editor for English-language newspapers.
"But Italy's development of freelance work is among the slowest in Europe" says Paola Gatto, a freelance translator-interpreter who has also attended the EFIP 2013 meeting on behalf of ACTA, which is member of the European Forum of Independent Professionals born in 2010 to represent independent working at EU level.
She is an adjunct professor in the Russian and Slavic studies department at New York University as well as a freelance Russian translator and interpreter and a poet.
