I do know what you mean. My 50-year old vibraphone (used on tour with Linda Ronstadt) has a drive belt and three different diameter drive wheels on the motor's shaft, so I can select the speed of the tremolo I want. It's actually not vibrato despite the name; it's tremolo (changes in volume). I think the player would have had to record the RealTrack with one or the other setting and BIAB cannot alter it. If you like a RealTrack but feel it should have been recorded by a different tremolo setting, you can make a request in the Styles Wishlist Forum. For MIDI, that's a question I can't answer but I've never encountered anything I could change, besides selecting a different patch for a vibraphone. My Roland MIDI synth offers several choices.

BIAB 2025 Win Audiophile. Software: Studio One 7 Pro, Swam horns, Acoustica-7, Notion 6, Song Master Pro, Win 11 Home. Hardware: Intel i9, 32 Gb; Roland Integra-7, Presonus 192 & Faderport 8, Royer 121, Adam Sub8 & Neumann 120 monitors.