Was the "shot heard round the world" fired in Lexington or Concord?

The "shot heard round the world" is part of a line in "The Concord Hymn," written in the 1830's by writer / philosopher Ralph Waldo Emerson for the dedication of a monument at the site of Concord's North Bridge.

"Here once the embattled farmers stood,
and fired the shot heard round the world."

No one can dispute Lexington's claim to the first shots, and sadly, the first colonial casualties of the Revolutionary War. However the "shot heard round the world" is not a reference to the first shot.

Emerson's poem is definately referring to the fighting at the North Bridge, where colonial militiamen were first ordered to fire on British soldiers, thus committing treason. Here also the first British soldiers were killed.

However, in a larger sense, was Emerson actually referring to a musket shot? Some argue that the true "shot heard round the world" is not a physical musket shot, but the ideals of liberty and self-determination.

It was for the defense of these ideals that people all over New England were roused into action against the British in April of 1775.