I noticed at each store there is a sign asking you to put the shopping carts back in the coral in the parking lot and they each do it with their own style.
Windmill Farms is a family-owned local store specializing in produce, organic items, and gourmet foods. I would describe their brand voice as Neighborhood Farmers Market.
Here's how Windmill Farms asks customers to bring shopping carts back. The message is friendly and folksy and they refer to their shopping carts as buggies. The message is signed with the owner's name.
Costco also sells food, just on a more extensive scale. I would describe their voice as Warehouse Luxury. They offer exceptional value on quality items.
A long legalese sign kindly asks you to return carts. It starts off with a with a mention of service: Our shopping carts are provided for your convenience. The notice ends with a commitment to price: help us keep our prices down. It basically says the same thing as the previous example, but you kind of get the feeling their lawyers had a hand in writing the sign.
Grocery Outlet store is another brand that emphasizes lower prices. I would describe their brand voice as Quirky Bargain. In contrast to the luxury items Costco carries, Grocery Outlet features end of stock and special purchases. If you save more than $100 on a purchase, they ring a bell and announce it on the loudspeaker to much whooping.
Notice how Grocery Outlet reminds you to remember your grocery bags, while Costco reminded you that by returning your cart, you help keep prices down.
Each of these brands stays consistent with their brand voice even in the most mundane (but highly visible) communications. One way you can keep a consistent voice is by selecting tone words that describe your brand. And then with every communication you write, hold it up to those tone words and see if your communication falls within these range of adjectives.
Brand Voice: Neighborhood Farmers Market
Tone descriptors: folksy, fresh, healthy, local, family
Brand Voice: Luxury Warehouse
Tone descriptors: quality, value, volume, service, corporate
Brand Voice: Quirky Bargain
Tone descriptors: bargain, fun, spirited, surprise, hunt
Try using tone words to keep your brand voice consistent.
Happy writing! :)