I believe I am the "Karaoke Jock" referenced by the OP. I went looking for my rather lengthy post from back then, with no results. Found a short one:
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A few things to remember that are different from DJing:
The emphasis is on the VOCALS, not the music. The music is used to ENHANCE the vocals. This means that instead of mixing professionally recorded music and vocals by pro musicians and singers, you must now mix studio "sound alike" music of constantly changing quality with amateur singers of varying talent. Vocal mixing alone is an art unto itself....
Resetting and mixing sound on the fly is a MUST. Remember, vocal emphasis, and each singer is different.
Microphone quality should be good ( the most popular is the Shure SM-58), but don't overkill ( Sennheiser or Shure Beta). A super great mic is also an unforgiving one, and you're singers are, for the most part, going to be in need of forgiving. On the other hand, if you have a great singer, it's wise to have a great mic on hand..
A good host will also set up with full accessibility to the crowd. No booth. In order to make people comfortable you must first make them comfortable WITH YOU. Gotta intermingle, meet and greet, answer a lot of questions, etc..
Good mic work ( but don't over do it)can be essential in helping to keep non-singers entertained, and in building a rapport with your singers in hopes of making them regulars.
Solving venue problems not normally directly connected to karaoke....
Meet and greet everyone- as any host would
Understand ALL that karaoke is- it has it's own psychology....
Run a FAIR rotation. This is is not negotiable. Screw it up and the you can lose the show.
In short, a good Karaoke Host must REALLY know how to multitask, or die trying.
THERE IS NO SUCH THING AS SPARE TIME in karaoke. If there is, you are doing it wrong. Time not at the controls should be used mingling and making acquaintances, if nothing else.
Just a few thoughts....
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It's very different from DJing if done correctly. On the other hand, if it gets in your blood you'll have the time of your life!