Daniel Spreadbury, Sibelius product manager, has posted a video dealing with percussion in Sibelius 5 using Sibelius Sounds Essentials.  The video covers the following:

    * Choosing the appropriate playback configuration in Play > Playback Devices
    * Adding percussion instruments when creating a new score or later using Create > Instruments
    * Using House Style > Edit Instruments to see which noteheads produce which sounds
    * Using the Mixer to understand which patch is being used to play back each percussion staff in your score
    * Using Create > Other > Instrument Change to switch between different percussion instruments on the same staff

http://www.sibeliusblog.com/archives/2009/02/15/video-tutorial-unpitched-percussion-sibelius-5/

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