Improv versus Sketch
Improvisation, or improv, is basically the art of making comedy on the spot. No script, no costumes, no sets, no props, and no one to tell you what to do (although some improv groups take suggestions from the audience). Improv is hard work. You need to stand on stage with next to nothing and no idea what you're going to do. All you have are your wits, your ability, and your experience. With these skills in hand you need just one more thing — trust. Trust in your fellow performers, trust in the audience, trust in yourself, and trust in knowing that things will just fall into place, because they have to.
With sketch, you know what's going to happen next. You know when to be funny and when to hold back. You know what line will be spoken next. And, if you've done the sketch before, you even know where the laughs should be. You also need to trust the script. The worst thing you can do is to get up on stage, doubt the script, and start trying to be funny at the expense of your fellow performers. Don't decide at the last minute that your part will be a lot funnier if you use a silly voice to deliver your lines — it won't. You need to have faith in the script and trust that it's funny as written.
Many comedy troupes develop a revue show that can run for several weeks with sketches that have been developed from previous improv shows. It's a great way to work the whole process out in front of a live audience and use improv-inspired ideas more than once. It allows those great “live” moments to “live” another day.
There can be a rivalry between improv and sketch performers, but a combination of the two can yield the best of both worlds. Use improv to get the ideas and the characters for sketches that can be developed further. Write sketches that are loose enough to allow for some improvisation so the actors performing it can use their talents to make the sketch better. A sketch can also be performed by a comedy duo or a solo performer. Many stand-ups see parts of their acts as sketches within a stand-up framework.