Some VST plugins effects you can use in Wavosaur sometimes need a tempo information in BPM.
Think about delay for example, with 1 BAR 1/2 1/4 1/8 etc..
So you may need to change the host tempo.
this is how you can do it in Wavosaur :
1. go to “Options” menu
2. open “Editor configuration”
3. type a tempo value i(n beat per minute) into the “VST host tempo” textfield
4. validate by clicking on “OK” button