Gospel music creates a celebatory mood by using a polyphonic texture, lots of instruments and hand clapping.
The polyphonic texture creates this mood because it is the heart of gospel music. Having multiple artist all performing one sound makes the music more exciting and makes people want to join in on the music.
The hand clapping creates a rhythm that makes people want to match what everyone else is doing. It also puts people in an almost "feel good" mode.
The instruments creates the background for gospel music mostly having drums. It helps gospel music stick to people more because some people can remember the tunes better than the chants.