Length is irrelevant. What matters is context - specifically a vague and nebulous dividing line between public service vs for-profit - and distinctiveness.<p>People have been sued for using very short but recognisable samples. In extreme cases some artists have negotiated a slice of the publishing just for contributing a sample.<p>(One of my favourite extreme examples is the Prodigy&#x27;s Firestarter from 1997, where an entire team of writers and producers negotiated a co-writing credit solely for the use of a very short sample of a woman yelling &quot;Hey!&quot;)