In 1966 the Slovenian branch of the Yugoslav broadcaster won the national selection and chose Berta Ambroz to sing song Brez Besed, written by Mojmir Sepe. The beautiful song has a appealing melody and nicely growing arrangement. Berta Ambroz gives a passionate, if somewhat shy performance also managing beautifully to use different nyances in her singing from delicate verse to a rousing refrain with a trembling vibrato in her voice. Song was definately one of the higlights of the 1966 contest.
The song fared rather well in the international final reaching the 7th place among 18 acts being one of the absolute best results for Yugoslavia until the victory 23 years later.
The 1966 Eurovision entry for Yugoslavia has a similar melody line than one of the most succesful entries, the famous Eres tu from Spain seven years later. For some reason this remained very much unnoticed at the time.
I could not find much information on the singer other than that she was only 21 years old when representing her country. Her entry is available in Spotify on a compilation album of her other hits (listen f.eg. her version of the James Bond tune Goldfinger) which gives an impression that she had before her death in 2003 some place in the Yugoslavian show business.
The composer-conductor Mojmir Sepe would, on the other hand, conduct the Eurovision orchestra four times in total, last time being as late as in 1998.
My points 4/5.