Possible Clues:

• Ten operas composed in largely unknown language
• An artificial tongue?
• Ten operas translated into language that's artificial
• Pet reason for developing an artificial language
• Extraordinary sense finally awoken in one inspiring language
• Artificial international language devised in 1887
• Language in which 'Hello, how are you?' is 'Saluton, kiel vi fartas?'
• Language that may get European parent so upset
• Language created by Ludwik Zamenhof in 1887
• Ten operas rewritten in artificial international language