Anacrusis

An anacrusis or upbeat occurs when a piece starts on a weak beat.

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Example:  Happy Birthday to you:  the first strong beat is on the syllable "birth".

Here is an example in simple triple time.  Listen for the first strong beat.

When counting a piece of music with an anacrusis, start with "and".

and 1 and 2 and etc

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The incomplete 'first' bar is rhythmically the final beats in the last bar.  So the final bar in a piece with an anacrusis will have fewer beats than suggested by its time signature (by the number of beats in the anacrusis).

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