adrianmcroft I Finally have my Bela BBB running my SFZ engine with the OSC / VST remote (64 + voices, filters, reverb etc).
Yes! (whatever SFZ is, but it sounds cool and a great achievement).
adrianmcroft Secondly, I need more storage for lots of funky Soundfonts - will Bela boot from the internal memory even with an SD card installed - or will it always boot from any available SD (I'd like to separate the 2 things : OS + Projects and Data).
that is explained here. Ultimately, as long as the SD card is non-bootable, it should boot from eMMC. I do remember that at least once I had troubles with this, and I worked around it by starting the partition on the SD card 8Kb into the disk. However, I never managed to reproduce the issue, so maybe it was just me being silly.
adrianmcroft I'm booting from the EMMC memory and would like to take a concrete copy of this for posterity - I'm so worried about losing years of fiddling that I wanted to check before opening Putty - can I blast the full image back onto an SD card or SFTP it to my PC ?
You could copy this file to your board, boot it from the eMMC with an SD card inserted (the SD card needs to be unbootable for this to work), and then execute it with:
FLASH_DESTINATION=sd bash -ex bela_flash_emmc.sh