if youre using audacity and the wav looks like the pic below then you have to do this

1. click the arrow that shows this menu and click split stereo track

2. should look like this now

3. then go on the menu for each track and select mono

4. should look like this now

5. once you export as ogg you will see this message

6. this is what it looks like when its saved, this will work in blockland

:D