Add a second synthesis engine — the format and switches already expect one #5

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opened 2026-08-18 01:34:38 +00:00 by bcox · 1 comment

bcox commented

2026-08-18 01:34:38 +00:00

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The codebase is shaped for more than one synthesis engine and currently has
exactly one (FmPairLayer). Adding a second is the extension the architecture
most explicitly anticipates.

What is already in place:

The patch format is additive. plugin/patch_format.h opens with it: a
reader skips any chunk it does not recognise, and layers are themselves
tagged and length-prefixed inside the layer chunk, "so a reader that has
never heard of a layer type can step over it rather than losing the rest of
the patch."
Switches over LayerKind are registration sites. .bazelrc sets
-Werror=switch precisely so a missed arm fails the build rather than
silently doing nothing: "a missed arm is an engine that silently does nothing
at that site rather than one that fails to build." Adding a kind will produce
a list of every place that needs teaching.
The matrix writer is factored for reuse. plugin/patch_format.h:295
notes the FM pair's record writer is arranged so "the next engine with a
matrix reuses it instead of" duplicating it.
Heterogeneous slots already work. Voice<kCapacity, Layers...> is
variadic over layer types; the single-engine case is just the current
instantiation.

So this is less "build an extension point" than "use the one that exists".
Whoever takes it should expect the compiler to enumerate the work.

The codebase is shaped for more than one synthesis engine and currently has exactly one (`FmPairLayer`). Adding a second is the extension the architecture most explicitly anticipates. What is already in place: - **The patch format is additive.** `plugin/patch_format.h` opens with it: a reader skips any chunk it does not recognise, and layers are themselves tagged and length-prefixed inside the layer chunk, "so a reader that has never heard of a layer type can step over it rather than losing the rest of the patch." - **Switches over `LayerKind` are registration sites.** `.bazelrc` sets `-Werror=switch` precisely so a missed arm fails the build rather than silently doing nothing: "a missed arm is an engine that silently does nothing at that site rather than one that fails to build." Adding a kind will produce a list of every place that needs teaching. - **The matrix writer is factored for reuse.** `plugin/patch_format.h:295` notes the FM pair's record writer is arranged so "the next engine with a matrix reuses it instead of" duplicating it. - **Heterogeneous slots already work.** `Voice<kCapacity, Layers...>` is variadic over layer types; the single-engine case is just the current instantiation. So this is less "build an extension point" than "use the one that exists". Whoever takes it should expect the compiler to enumerate the work.