Adaptations and translations of songs

This  could  be  opening a can of worms but  can any  one  explain the  legality's  of  adapting  or  translating  a  song  from a  foreign language .
Here in Greece  we  have  some  great  tunes with un translatable lyrics. Due to  the structure  of  the language straight  translation doesn't  often make  sense  in a  song  or  fit  into  English phraseology .
So  what  I am asking  basically  is  how do  the  copy right  laws  affect a piece  of  work that  has  been  adapted  from an existing song .I would  expect  permissions  would  have  to  be  sought  from the  writer of the  original  song to  use  the  music and  also  he  or  she  should  be  credited   with  the  writing despite the fact  that  the  wording   may  have  been changed  partly  or  even completely . 
I  refer to  songs  like la bamba which  became twist and  shout  and  holiday  songs  like  una paloma blanka .
My  reasons  for asking  this  question is  that  I  have  recently  adapted to  English a  song written by  Pavlos Pavlides  called Treno Fantasma (Ghost  Train)and  I  feel it wouldn't  be  ethical to publish the adaptation with out  first finding out the legality's and  secondly approaching  Pavlos  for  his permission .