Rhodes Vibrato disabled?

Such fine sounds, but: using the free (ad-supported) version, the Vibrato has no audible effect at any setting for the Rhodes instruments [Suitcase / Stage / Dyno / Ex]. The Wurli Vibrato works as expected.
Bug?
User error? (Yes, I turned it On as well as adjusting Intensity & Speed!)
Only available as an In-App purchase?

zspoppa about Neo-Soul Keys, v2.2.3