If you can get everybody singing together, that is something that really unites a group of people. Play the National Anthem of the United States in the foreign country (say when we win a gold medal at the Olympics) and see how it unites our citizens. Play “Take Me Out to the Ball Game” at the 7th inning stretch. Sing Happy Birthday even in a crowded restaurant. Sing “Hang On Sloopy” in Ohio. Put a quarter in the jukebox at the local VFW and play “You Don’t Even Call Me by My Name.” Do any of these and you will see people united with a common voice and in a common cause.
If you understand that, you understand why there is an opening song at Mass. The opening song is part of the Mass. It is not like the opening song of a sit-com that, if you miss it, you really haven’t missed anything. If you miss the opening song, you’ve missed part of the Mass. Paragraph 47 of the GIRM states that the purpose of the opening song, “is to open the celebration, foster unity . . . and introduce their thoughts to the mystery of the liturgical time or festivity . . .” Only lastly does it list one of its purposes to be that of accompanying the priest and the ministers to the altar.
In all of this, we see that this is really the first opportunity at the Mass for the corporate Body of Christ to worship Him. So even if you don’t like your voice – God gave it to you – give it to Him back.