This is the core-business of Bart at work. Most of our gigs involve at least some multicamera work.
Recording keynotes works perfectly well with one camera. But can you actually read what's on the slides? Or see the expression on the presenter's face when he announces something important? Probably not...
That's why we always advice to use at least two camera angles (a close up of the presenter and a wider shot) as well as a full screen recording of the slides. This gives us three sources, between which we cut according to the story. You'll always be able to read the slides, see the overall atmosphere and catch every raised eyebrow.
And: cutting between multiple sources makes the video more dynamic and gives it a much more professional look.
We can even add a fourth source. Maybe a second close up camera when there is a panel on stage. Or perhaps a 'reverse' angle, showing the audience. Ideal for Q & A sessions or those crowded room / applauding audience shots!