He has the ability to influence other dogs to be sleepy when he sings his song.
Barlow spent most of his life outside the Big Easy Hotel along Route 66, lazing in the sun, and howling alongside a Banjo Player who often visited the hotel. When the hotel closed down, Barlow was left on his own; Apparently, the owner of the hotel was not Barlow's owner.
When Barlow was brought to Shelter 17, he began sharing his philosophy with the dogs there, causing them to become lazy and slothful. When the same Banjo Player whom Barlow sang with arrived at the Shelter with his granddaughter, Barlow recognized him. When the Player and his daughter left, due to all the dogs being boring, Barlow realized his mistake, and with Lucky's help, managed to get himself adopted.