what you mean? synthesisers are software... I think the context is clear here and we're talking about software made for music, so the usage of patch is accurate. If author wanted to use "patch" to mean patching a file they would likely be specific or context could be inferred.

"A patch is data for modifying an existing software resource such as a program or a file"

Which is what patching synths/drum machines (and files) does.