VARCHAR to TIME

hi,


I have a couple thousand mp3s with all their properties stored in a
table... the songlength is currently saved as varchar... now, after the
database is filled the thought crossed my mind to get the overall
playlength... well, a "sum()" won't work on varchars, obviously...

now, I'd like to port the varchars to the time format.. could someone
give me hints on accomplishing this task?

TIA


  length      | character varying(10)  |


  SELECT length FROM tmp3 ;
...
  02:11
  04:19
  02:04
  03:36
  04:09
  04:08
  01:55
...