Stefan,
SoundDiver is excellent for controlling the jv1010. I use it in conjunction with XG-Works 3.05 (sequencer) and Yamaha's SW1000 soundcard. The big problem with Sdiver is that it is extremely fiddly to configure it for parallel use with your sequencer. I have got mine up and running that way now, and if you go to http://www.egroups.com/messages/sounddiver-users
and have a look at my posting 5116 you should be well on your way towards jv1010 control bliss! While at this site you will do well in performing a search on Hubi or Hubi's, since the key to blissful SoundDiving in parallel with sequencing is Hubi's Loopback Device (freeware).
Remember: It took me quite a while to set things up so that they work - I dare say it is worth the effort...
All the best,
Magnus