A little research, I thought I would share
“Louder than all trumpets sounds his (Pan’s) voice alone, and at that sound fall helm and sword, the charioteer from his rocking car and bolts from gates of walls by night; nor might the helm of Ares and the tresses of the Erinyes, nor the dismal Gorgon from on high spread such terror, nor with phantoms so dire sweep an army in headlong rout.” Valerius Flaccus, Argonautica 3. 46
“(Pan) is said to have had a terrific voice (Val. Flacc. iii. 31), and by it to have frightened the Titans in their fight with the gods. (Eratosth. Catast. 27.)”. Source: Dictionary of Greek and Roman Biography and Mythology.
More clearly Theon of Alexandria (1st century BC) says.
“the god Pan struck terror into the hearts of the giants, when they warred against heaven, by blowing into a sea-shell.”
PS, any one know a primary source fot Pans involvement in the Titanomachy or Gigantomachy?