In my working with scopes I just tend to tune the scope to A and play A's and harmonically related notes which also appear either stable or moving very slowly. This works very well in Smexoscope and even if the wave drifts left and right a bit due to u-he synths being real analogue (.......
Also, you know what would be awesome? The u-he 'scope as a separate plugin with the option to make it bigger and change the wave colour! I use smexoscope at the moment, but overall the scopes in ACE etc are a lot sexier IMO.
What do the other wavegazers think?
