Smokey Robinson knew the trick. So did Keith Richards. They know how to grab an audience in a couple of seconds. People of a certain age (actually, people of many ages) only have to hear Keith's first two fuzzy notes of "Satisfaction", or the six bell-clear notes from Marv Taplin's guitar on "Tracks of my Tears" and they're hooked.
OK, some of the emotion when you hear a song now comes from the familiarity, and memories it evokes. But there are some openings so good that the first time you hear them, you want to hear more. That's not only the secret to a great song, it's also the secret to a great speech.
If you can evoke a strong emotion in the first few seconds, your audience will be with you for the rest of your delivery. However, if you stumble to the mike, slightly embarrassed at your introduction, and begin with a phrase like "I'll do my best to tell you something of interest", then you may as well forget it and walk off again.
You need to seize the opportunity, make a promise of great things to come, and then launch into the melody. Still don't believe me? Then watch this -