You should always rehearse what you will say because if the audience likes you, they will like the music. If they don't care about what you're saying or the way you're saying it, they won't care for the music. Here are the four basics of onstage speaking.
- Tone of voice: If you ever had to introduce your fellow musicians, you know how boring a list of names gets. The number one mistake people make is have their voice go down in intonation at the end of each name. Keep your voice going up every time you end a sentence.
- Energy: If you speak on stage the same way you do at home, it will come across as if you'd rather be home. Think of your voice in terms of dynamics: your regular speaking volume is p or mp, so make sure to bring it up to at least mf on the stage. The longer you speak, the more volume and excitement you need to bring forth.
- Stories: If you simply state facts such as players names and titles of songs, your audience will think that you are speaking because you have to and not because you want to. That's why you need to share a few real life stories. It can be anything from the time your band lost the music of the piece you're about to play, to how a tornado alarm went off in the middle of that song, etc.
- Your body speaks too: Don't look at the floor, or just at the other performers. Stand tall, ground your two feet to the ground and look directly at your audience. Make sure to finish your speech before you sit back down, or before you walk to your spot.
Picture from http://sheilagranger.blogspot.com/2011/01/hypnotherapy-for-public-speaking.html