I assume you mean the cocktail hour before the wedding "reception" ? ...
Depending on the wishes of the client, venue, crowd, etc it could be laid back bossas, light jazz, standards, OR it could be a "warmup" for the party, with more lively music ... Either way, vocals (even at a low volume) are a part of my repertoire ...
If you ARE referring to a cocktail hour before the "ceremony" I think it would be more subdued ...
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