According to the author of 1 Chronicles, King David wore special clothes made of fine linen, just like the people carrying the important box and those singing. This shows how everyone dressed nicely and carefully to show respect and happiness during this important event.
1 Chronicles 15:27: And David [was] clothed with a robe of fine linen, and all the Levites that bare the ark, and the singers, and Chenaniah the master of the song with the singers: David also [had] upon him an ephod of linen. [song: or, carriage]
In this verse, David is described as wearing a linen ephod, contradicting the idea of him wearing a robe of fine linen as stated in 1 Chronicles 15:27.
2 Samuel 6:14: And David danced before the LORD with all [his] might; and David [was] girded with a linen ephod.