TubeNet

okay, what kind of souza is this ?
http://www.youtube.com/watch?v=ymzXYGDXMNk" target="_blank" target="_blank
looks like a Eb ..... but what do I know...

Based on the leadpipe, it's likely something of Russian design. Strange looking, but it may be more comfortable? He's using BBb fingerings.

The very long lower neck goes into a long main tuning slide that sits on top of the valve slides, reversed Buescher fashion when it comes to the direction of the airflow.

Also this sousaphone is full circle with a fairly standard diameter. I tend very much to doubt that any pitch but BBb could provide tubing enough for what we see here.

Klaus