Your director is not a boot-camp sergeant but his or her directions are vital to making a song musical and coherent. Your director will guide you in

• dynamcs (the loudness or softness of a piece)
• mood (the overall sound of a piece)
• entrances at the beginning of a piece or tricky line starts
• endings of lines or verses
• breaks for instrumental verses
• and much more.

Follow your director meticulously to avoid mistakes.