As a society, we have become pretty casual. Nothing wrong with that, but weddings are one of the few things left that are still rather formal. Women wear nice dresses to weddings. Even the most casual of men wear a jacket and button down shirt. A wedding gives everyone a reason to consider their own relationships and there is always a bit of anticipation in the air.
During a sales presentation, I'll ask brides about the moments leading up to the ceremony. I explain that attendees are dressed up and there is excitement about seeing friends and cousins they haven't seen in a while and even old married couples are flirting with each other a bit because they have a special occasion for which to get dressed up. I'll ask brides, "What kind of music do you hear as your guests are arriving before the ceremony?" Owing to the formal nature of the occasion, classical music SPEAKS the moment. Even for people who don't know classical music very well, it feels familiar to them. It adds body and life and it compliments those feelings of anticipation.
People, individually, are pretty smart, but crowds, collectively, have a separate mentality and they need to be told what to do. I like to have the music provide the instructions so that the DJ or wedding minister doesn't need to speak any instructions. If the background music has been strings, I like to switch to a piano song and turn it up 15% to signal the start of the formalities. If it has been piano music, I like to switch to classical guitar and turn it up 15%. People know that something is different and they quiet down and sit up straight in their seats and turn their attention to the entrance of the bridal party without being told specifically to do so. The oft-overlooked background music has spoken it.
A mistake that many DJs make is #1) being too loud in general and #2) not taking advantage of the natural energy of the crowd and the occasion and then, not using good musical selections to enhance that energy. There will always be several animated and electric conversations going on and those conversations add to the energy of the space and that is a good thing! When a spoken announcement cuts into that, it can be jarring as people have to disconnect from their conversations to hear what is being said and then they will be more disruptive to the announced instruction as they now attempt to finish what was being said ANYWAYS! However, if the music speaks it, it can be far more profound and effective at quieting those conversations more naturally and having attendees direct their attention to the matter at hand- like the officiant and groom having taken their places in advance of the ceremony.
I like to keep the music about 5% below whatever the current level of conversation is in the space. I understand that a few voices rise specifically in response to the level of background music but please don't bust my chops over that issue. I've been around the block enough times to know how to gauge the level of music. I contend that more people raise their voices because they are excited and they feel comfortable being animated and gesturing largely with their hands and speaking excitedly. They want to be heard and they want to speak freely, but they would be embarrassed being heard above anybody else. The music needs to be there to mask each voice so that no single voice ever rises above the overall volume and people can feel comfortable being so animated.
Please take this next part as it is intended- with a smile. Most hotels and golf/racquet clubs have music playing in the restrooms. There are certain sounds that are rather satisfying to make in a restroom, but entirely unpleasant to hear or to worry about being heard. Background music masks it- thus adding to your comfortable experience.
I use a computerized DJ system that can play background music automatically with playlists that I have defined and I also determine how I want the computer to mix it and how many seconds each song will overlap with the next one. During automated background music, every once in awhile, a song may have a long "fade." The song may be effectively over, as it has faded from the range of hearing, but the computer does not know to start the next song because the file hasn't approached its actual end- it's still fading. As the music falls silent for 6 or 7 seconds before the next file plays, you'll see and hear a few of the animated conversations go into a brief pause, waiting for that next song before they can finish the exciting thing they were talking about because they don't want their voice to be heard above the rest. I usually make a mental note of such a song and edit it during the week to end a bit sooner so that the next song starts at the "effective" end and not the "actual" end for future airings. If a radio DJ ever spoke or played a commercial over the long fading "strike" piano note at the end of the Beatles' A Day in the Life, even though the song is effectively over, I'd have to call up the radio station and threaten a boycott of some sort.
Side note- during the dancing portion, I always mix live because there are several simultaneous queues that I may not want triggered automatically. I may want a lighting effect and a pose or hand gesture along with a dramatic musical element all timed exactly when I want them not when the computer thinks I may want them. I saw rock group "Styx" recently and witnessed a few such "Spinal Tap" moments. It was the second night of the tour and Tommy Shaw stepped up to his spot after the second song and shouted "Hello Friends!" and a computer triggered spotlight illuminated a empty mic stand on the other side of the stage. For my purpose, during most background music applications, such queues are not as crucial.
Another important element of background music is the flavor and the energy level of it. The ceremony portion may have one musical "flavor" and then the cocktail hour may be some traditional music that represents an ethnic heritage, the dinner hour may have yet another flavor. During dinner, does the customer want classic standards mixed with new school- Sinatra/Rod Stewart/Michael Buble? Or perhaps something more contemporary like Jack Johnson/Dave Matthews/Jason Mraz? Latin guitar? Old Jazz mixed with some Classic R&B? Classic rock like Van Morrison/Beatles? Properly selected background music will take the guests from what has been a formal ceremony to what will be a dance party after dinner without the DJ saying something stupid like "Yo people! Get up out ya seats!" The background music will have taken them there and naturally created an energy level conducive to dancing and they will fly out of their chairs and dance.
I like music that is rhythmic but not necessarily a vocal. For many of the reasons already described, a sung lyric may inadvertently disconnect people from that electric conversation as they tune in to the song lyric and tune out of the moment they are having at the table. I also generally avoid "elevator muzak" where all elements of a familiar song are intact but with a saxophone taking what would have been the lead vocal. It's vapid and it can still have the same effect of people tuning in to the music and out of their moments.
At about the time that the last table is served dinner, I begin to switch ever-so-slightly from background to dance music even though I don't really want anybody to dance before the bride and groom officially open the dancefloor with their first dance.
A song like "My Girl" by the Temptations is somewhere in the middle. It's a well known song, rhythmic, has a memorable vocal and it begins to naturally help people wrap up their conversation and disconnect from it and turn their attention to what will be a more communal experience as we celebrate the wedding with 3 generations of people out on the dancefloor dancing to the same song- together. After a couple of songs like that, I'll start to see tapping toes and snapping fingers and I'll see some attention starting to turn to me waiting for some direction on what to do next. At that point, it IS the intention to disconnect from those conversations. The energy that is lost as those conversations come to a close will be replaced with the energy that is contributed to the space by a packed dancefloor. Strangely, this will be the first introduction of the abilities of the DJ even though I will have provided a lot up to this point.
Here's a recent pic of me imparting some sage wisdom to the masses on a couple of cool dance steps. The magic really happens when the crowd and the DJ become one. People are out there dancing and getting into it, hugging each other, singing along with every word and they send that energy to me and I feel it and I dig down a bit deeper and amp it up and send a renewed energy back to them and they feel it and they get down and they send it back to me and I send it back to them... it's a party!