Hi Mark,

quote: I think Fred may have pointed to the solution. Thanks for the tip, Fred.

I think that may be the only requirement.

I opened the files I just uploaded and the sostenuto worked properly. I then split the hands and it had no effect on the sustain. Both staves contained the pedal graphs. I then erased the graphs from the LH staff and played only the left hand. Without the graphs in the LH, it continued to play the sostenuto properly. So, it appears that the most important thing is the "Normal Sustain" option. The pedal graphs are only necessary on one staff.

Cheers,
Fred