Two kinds of performance styles are "Concert" and "Background".
Concert Style is where an audience is attentive to you the entire time. Then, you do all the staging, narration, jokes and whatnot that make the most engaging performance you can make. For concerts, audience response is predictable, whether it's the wild dancing cheers of a hard rock concert, or the retrained quiet of classical chamber music applause or anything in between. Nearly everything in a singer's training, craft and technique assumes you're doing concerts.
But there are times where the audience is changing, or have other things to do while you perform. Outdoor gigs in entryways or walkways often are like this: people have business to do and can enjoy you at most for a few minutes, then on they go. If folks are mingling over drinks or dinner while you're performing, they might listen a bit, and even shush each other so they can pay attention to you, but the social pressure to mingle often rules the room and it seems you're not a center of attention.
This is were you use "Background style", where all you do is sing the songs beautifully and smoothly without demanding that anyone pay much attention. In these, you don't do the patter, moves or jokes, just sing pretty and look pretty as you can. This removes the pressure of the audience to split their attention for you and leave it on each other. If people are noisily chatting, you don't try to overcome them with loud music: all they can be louder than all you. Rather you simply make relatively soft, beautiful background music and sing "under" the noise. Think "Elevator Muzak"
Background style gigs can be disheartening. Passersby mostly look away from you, and the room seems devoted to ignoring you. Maybe you are being slighted or taken for granted, and you'd wonder why, with all your talent and preparation, you are doing THIS. Still, if this is a paid gig, remember that someone has made your music a gift for these people. Give it. By all means, smile and sing well, despite the apparent put-down. There is one little artistic reward: it's rather like an open dress rehearsal for the music only.
One variation of the background gig is the "Table stroll", used where the room is large and filled with chatty people and there is no way the people on the far side of the room can hear you. What you do is move your group from area of the room to area of the room every few songs. By the end of the set, you might have walked all around the room so that, while no one there heard everything, everyone heard something. This turns a "background" gig into a series of mini-concerts.
Sometimes a booking changes from "background" to "concert" if an audience gathers, or you find a few people who are very interested in what you are doing. While they're there, you do a "concert", then when they disperse, you go back to "background" style. Shifting to "concert style" or to "background" requires the Emcee and director notice who is listening or not and how intently, then make a judgement call which to do. When in doubt, use "background style". If it's clear the audience is responding to you, switch over to concert style, then back when they are not.
This all comes down to giving your customers what they need and want, whether it be a blowout enthusiastic concert, or simple songs to set a mood.