If you have configured Snack to use the NIST/Sphere file format you have
to explicitly add this file format in your script using the
'package require snacksphere' command after 'package require snack'. 
This will make Snack automatically recognize this file format in addition 
to those already built-in, such as WAV, AU, and AIFF. 

Writing the Sphere file format is not supported yet.

See ../demos/SphereTest.tcl for an example.
