Obviously you can do it by using a MIK file format karaoke editor. The KED is a freeware MIK karaoke editor: you can download it here, but as MIK file format is freeware, new editors may come out soon!
But remember you can use the KAR to MIK converter function of the 3.0 and 98 versions, to convert KAR files easily available in Internet (see the Mikey Links page)!