English translations for the operatic terms 二流 and 倒板?
I would argue that it is wisest to simply transliterate (with Pinyin) with the Chinese characters included. As both these are specific terms with no equivalent in Western culture, transliteration with some explanation is best. For example:


  erliu (二六, a medium tempo xipi tune)
  
  daoban (倒板, literally "lead-in meter")


However, academic studies have provided standard translations:


  二六 = two-six meter
  
  倒板 = lead-in meter