Multiple consecutive presentations without showing desktop?

Other applications have a playlist feature, or hyperlink each file together, Keynote does not have these tools.

Instead, make one consolidated Keynote presentation. Test before using as occasional glitches occur with very large file sizes.

A workaround is to blank the projector before opening the next presentation (using the projectors mute, blank or black facility) then switch back to projection again when completed. Thats how cinemas used to switch film reels and still perform the same procedure when changing video files today.

Keynote from iWork '09 can do this. The new Keynote inexplicably removed this very-handy, fantastic feature. In iWork '09 Keynote, in the Inspector, the hyperlink menu has the option of hyperlinking to another Keynote slideshow. To link one slideshow (song background, in your case) to the next, simply click any object or textbox in your last slide (or every slide, if you want) and then select-all. In Inspector, go to the hyperlink menu, choose to hyperlink "to another Keynote file," and then navigate to select which Keynote file is next. When you need to do the presentation, open all Keynote files that are linked. Then, play your first file. When it's time to link to another slideshow, you mouse and click any object or textbox on the slide (yes, the mouse hand appears when you move the mouse), and the other slideshow opens (and automatically plays if you've set it to do so) without anyone watching it seeing your desktop. The advantage of linking separate slideshows over creating one big one is that you can do something like this (this is what I do each week): have a slideshow that plays automatically with a songlist that rolls over and over indefinitely (while people arrive) and then seamlessly links (when I want it to) to another automaticIy playing slideshow with no music (which plays behind me while I give an introduction and announcements), and then goes (through a hyperlink) to a third slideshow that is one that I need to advance by click (not automatic) as a narrated presentation. If you want, you can link that narrated slideshow to a fourth and different, automatically playing, indefinitely looping slideshow with the same or different playlist (or none) out of iTunes for post-presentation time "atmosphere." You can't do this kind of of thing--have this kind of variance--with a big, conglomeration file. I still use iWork '09's Keynote because I use this particular feature in multiple ways every week in presentations. And, yes, every time a new version of Keynote arrives, I check and see if they've added this feature back to it. That's why I'm in the discussion forum today. So far, no. If you want to do this and don't have the iWork '09 CD/DVD, you can purchase it on eBay from someone.

Keynote from iWork '09 can do this.

Indeed it can, although a previous version of an application had certain features, it doesn't mean current software has the exact same toolset.

The new Keynote inexplicably removed this very-handy, fantastic feature.

It was not removed, it was never included in any of version 6 series.

Linking files in version 6 series filetype was identified as a security weakness.

every time a new version of Keynote arrives, I check and see if they've added this feature back to it.

I can't speak for Apple, but I would guess this isn't going to be re-introduced with the current filetype being used.