The dove tail slot is in the body, and the dove tail is cut on the end of the neck.  That little V shaped bit of wood is all that resists the string pressure keeping the neck in line.  That pull can be in the area of 230 to 250 lb depending on the gauge of strings.

The quality of the joint also effects the sound as some of the sound vibration come down the neck, through the joint, and into the body of the guitar.