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 Sphere files is not supported yet.

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