There are a number of commands in the mod-host protocol that I would like to be able to call (or emulate) from an LV2 plugin, allowing this plugin to control various things, for example:
Is it possible to do this? (Or is there another API that has similar capabilities that can be used
no, and it is not wanted to be honest.
there are several layers at play for managing the state of the pedalboard, messing with its internals is bound to cause issues.
OK Can the mod-host (or similar) protocol be called from a shell script or is it ‘dead’?
I recall reading about plans to introduce a rest API, is this still on the cards?
how is that different?
mod-host is still the host in use. the one in control of the pedalboard session is mod-ui.
no immediate plans to change things related to reworking internals.
any method to have plugins control other completely unrelated plugins is bound to randomly break in an update, because it is not an officially supported thing.
OK.
So the only supported approach for one plugin to influence another is via MIDI with virtual MIDI loopback enabled or CV?
yes. unless you control 2 or more plugins, and thus can have your own internal protocol of sorts. this is how the portal plugins can know when both sides of the portal are active.