diff --git a/src/vst/ivsthostapplication.rs b/src/vst/ivsthostapplication.rs
new file mode 100644
index 0000000..3ea35f7
--- /dev/null
+++ b/src/vst/ivsthostapplication.rs
@@ -0,0 +1,47 @@
+use crate::base::{tchar, tresult, TBool};
+use crate::vst::IMessage;
+use vst3_com::interfaces::iunknown::IUnknown;
+use vst3_com::{com_interface, IID};
+
+#[com_interface("E564A636-6A8B-8CAF-DB2D-496958E595CC")]
+pub trait IHostApplication: IUnknown {
+    unsafe fn get_name(&self, name: tchar) -> tresult;
+    unsafe fn create_instance(
+        &self,
+        cid: *mut IID,
+        _iid: *mut IID,
+        obj: *mut *mut c_void,
+    ) -> tresult;
+}
+
+#[inline]
+pub unsafe fn allocate_message(host: *mut dyn IHostApplication) -> Option<*mut dyn IMessage> {
+    // TODO: Impl the FUID class first for Interface::iid.to_tuid to work
+    let mut iid: IID = Default::default;
+    // IMessage::iid.to_tuid(iid);
+    let m: *mut IMessage = std::ptr::null_mut();
+    if (host.createInstance(iid, iid, m as *mut *mut c_void /* or invoke as_mut_ptr()? */) == kResultOk) {
+        Some(m)
+    }
+    None
+}
+
+#[com_interface("61AC6ED3-85BB-7BB9-1D1C-47E229633AEC")]
+pub trait IVst3ToVst2Wrapper: IUnknown { }
+
+#[com_interface("44AA97B6-91B0-0B6F-C095-4688A3B8C6C5")]
+pub trait IVst3ToAUWrapper: IUnknown { }
+
+#[com_interface("C6F4BE93-2CB3-1B95-60C5-62426D319DC6")]
+pub trait IVst3ToAAXWrapper: IUnknown { }
+
+#[com_interface("E39F35F7-0088-50B7-42CF-4BF944149067")]
+pub trait IVst3WrapperMPESupport: IUnknown {
+    unsafe fn enable_mpe_input_processing(&self, state: TBool) -> tresult;
+    unsafe fn set_mpe_input_device_settings(
+        &self,
+        master_channel: i32,
+        member_begin_channel: i32,
+        member_end_channel: i32
+        ) -> tresult;
+}
diff --git a/src/vst/ivstinterappaudio.rs b/src/vst/ivstinterappaudio.rs
new file mode 100644
index 0000000..24b6a5c
--- /dev/null
+++ b/src/vst/ivstinterappaudio.rs
@@ -0,0 +1,32 @@
+use crate::base::{tresult, TBool};
+use vst3_com::com_interface;
+use vst3_com::interfaces::iunknown::IUnknown;
+
+// Defined elsewhere
+struct ViewRect {};
+struct Event {};
+
+#[com_interface("FDC8CDE2-28AE-D45B-68DF-415E0CE5743D")]
+pub trait IInterAppAudioHost: IUnknown {
+    unsafe fn get_screen_size(&self, size: *mut ViewRect, scale: *mut f32) -> tresult;
+    unsafe fn connected_to_host(&self) -> tresult;
+    unsafe fn switch_to_host(&self) -> tresult;
+    unsafe fn send_remote_control_event(&self, event: u32) -> tresult;
+    unsafe fn get_host_icon(&self, icon: *mut *mut c_void) -> tresult;
+    unsafe fn schedule_event_from_ui(&self, event: &mut Event) -> tresult;
+    unsafe fn create_preset_manager(&self, cid: *const IID) -> Option<*mut IInterAppAudioPresetManager>;
+    unsafe fn show_settings_view(&self) -> tresult;
+}
+
+#[com_interface("CFD5D6D7-95B0-B50D-5FC2-4AA16020C72D")]
+pub trait IInterAppAudioConnectionNotification: IUnknown {
+    unsafe fn on_inter_app_audio_connection_state_change(&self, new_state: TBool) -> tresult;
+}
+
+#[com_interface("DDEF3FC9-B4B3-809A-46C9-4E1DADE6FCC4")]
+pub trait IInterAppAudioPresetManager: IUnknown {
+    unsafe fn run_load_preset_browser(&self) -> tresult;
+	  unsafe fn run_save_preset_browser(&self) -> tresult;
+	  unsafe fn load_next_preset(&self) -> tresult;
+	  unsafe fn load_previous_preset(&self) -> tresult;
+}
diff --git a/src/vst/ivsttestplugprovider.rs b/src/vst/ivsttestplugprovider.rs
new file mode 100644
index 0000000..2f9d8ab
--- /dev/null
+++ b/src/vst/ivsttestplugprovider.rs
@@ -0,0 +1,13 @@
+use crate::base::tresult;
+use crate::vst::{IComponent, IEditController, IStringResult};
+use vst3_com::com_interface;
+use vst3_com::interfaces::iunknown::IUnknown;
+
+#[com_interface("BAB58FD6-8F97-6E1E-4E99-430F86BE70EE")]
+pub trait ITestPlugProvider: IUnknown {
+    unsafe fn get_component(&self) -> Option<*mut IComponent>;
+    unsafe fn get_controller(&self) -> Option<*mut IEditController>;
+    unsafe fn release_plugin(component: *mut IComponent, controller: *mut IEditController) -> tresult;
+    unsafe const fn get_sub_categories(&self, result: &mut IStringResult) -> tresult;
+    // unsafe const fn get_component_uid(uid: &mut FUID) -> tresult; TODO: FUID
+}
diff --git a/src/vst/mod.rs b/src/vst/mod.rs
index 3f98e03..90633f8 100644
--- a/src/vst/mod.rs
+++ b/src/vst/mod.rs
@@ -6,6 +6,8 @@ mod ivstcomponent;
 mod ivstcontextmenu;
 mod ivsteditcontroller;
 mod ivstevents;
+mod ivsthostapplication;
+mod ivstinterappaudio;
 mod ivstmessage;
 mod ivstmidicontroller;
 mod ivstmidilearn;
@@ -17,6 +19,7 @@ mod ivstplugview;
 mod ivstprefetchablesupport;
 mod ivstprocesscontext;
 mod ivstrepresentation;
+mod ivsttestplugprovider;
 mod ivstunits;
 mod vsttypes;
 
@@ -28,6 +31,8 @@ pub use ivstcomponent::*;
 pub use ivstcontextmenu::*;
 pub use ivsteditcontroller::*;
 pub use ivstevents::*;
+pub use ivsthostapplication::*;
+pub use ivstinterappaudio::*;
 pub use ivstmessage::*;
 pub use ivstmidicontroller::*;
 pub use ivstmidilearn::*;
@@ -39,7 +44,8 @@ pub use ivstplugview::*;
 pub use ivstprefetchablesupport::*;
 pub use ivstprocesscontext::*;
 pub use ivstrepresentation::*;
+pub use ivsttestplugprovider::*;
 pub use ivstunits::*;
 pub use vsttypes::*;
 
-//todo: ivsttestplugprovider, test/itest vstspeaker.h,
+//todo: test/itest vstspeaker.h,