Borderline Cases

Some recordings which include brief examples of the human voice are typically considered instrumentals. Examples include singles with the following:

• Short verbal interjections (e.g. "Tequila" or "Wipe Out" or "Topsy");
• Repetitive nonsense words (e.g. "Woo Hoo" or "Uh! Oh!");
• A short spoken Passage (e.g "To Live is to Die" by Metallica or "Gonna Fly Now" by Bill Conti );
• Wordless vocal effects (such as drones (e.g. "Rockit");
• Vocal percussion such as beatbox B-sides on rap singles;
• Yodeling (e.g. "Hocus Pocus");
• Whistling (e.g. "I Was Kaiser Bill's Batman" or "Colonel Bogey March").

A few songs categorized as instrumentals may even include actual vocals, if they appear only as a short part of an extended piece (e.g. "TSOP (The Sound of Philadelphia)").
Sources www.wikipedia.org