@J-M-L @jfjlaros and a7 (only allowed to tag 2 people properly as I'm new, sorry!) thanks very much for respective input. I've wired up circuit, uploaded code (which works beautifully, thank you), and tomorrow am going to construct a little perspex platform to transmit the vibration (omitted by speaker) across substrate of samples I use. Will post link to preprint of paper that this project is used in, by early October. Full paper may take a couple of months after that, but will post here too when done.
Again, please let me know if you would like to feature in preprint/ paper. I'll default to linking to this thread and acknowledging input from forum, otherwise.
Cheers.