diff --git a/src/core.rs b/src/core.rs
index 7474b042..5fc218a7 100644
--- a/src/core.rs
+++ b/src/core.rs
@@ -34,7 +34,7 @@ submod!( handle midi render time );
 pub type Usually<T> = Result<T, Box<dyn Error>>;
 
 /// A UI component.
-pub trait Component: Render + Handle {
+pub trait Component: Render + Handle + Sync {
     /// Perform type erasure for collecting heterogeneous components.
     fn boxed (self) -> Box<dyn Component> where Self: Sized + 'static {
         Box::new(self)
@@ -42,7 +42,7 @@ pub trait Component: Render + Handle {
 }
 
 /// Anything that implements `Render` + `Handle` can be used as a UI component.
-impl<T: Render + Handle> Component for T {}
+impl<T: Render + Handle + Sync> Component for T {}
 
 /// A UI component that may be associated with a JACK client by the `Jack` factory.
 pub trait Device: Render + Handle + Process + Send + Sync {
@@ -61,11 +61,11 @@ pub use crate::{submod, render, handle, process, phrase, keymap, key, ports};
 // Reexport JACK proto-lib:
 pub use crate::jack::*;
 
-impl<T: Render + Handle + Send + Sized + 'static> Run for T {}
+impl<T: Render + Handle + Send + Sync + Sized + 'static> Run for T {}
 
-pub trait Run: Render + Handle + Send + Sized + 'static {
-    fn run (self, init: Option<impl FnOnce(Arc<Mutex<Self>>)->Usually<()>>) -> Usually<()> {
-        let app = Arc::new(Mutex::new(self));
+pub trait Run: Render + Handle + Send + Sync + Sized + 'static {
+    fn run (self, init: Option<impl FnOnce(Arc<RwLock<Self>>)->Usually<()>>) -> Usually<()> {
+        let app = Arc::new(RwLock::new(self));
         let exited = Arc::new(AtomicBool::new(false));
         let _input_thread = input_thread(&exited, &app);
         terminal_setup()?;
@@ -106,7 +106,7 @@ pub fn terminal_teardown () -> Usually<()> {
 /// Main thread render loop
 pub fn main_thread (
     exited: &Arc<AtomicBool>,
-    device: &Arc<Mutex<impl Render + Send + 'static>>
+    device: &Arc<RwLock<impl Render + Send + Sync + 'static>>
 ) -> Usually<JoinHandle<()>> {
     let exited = exited.clone();
     let device = device.clone();
@@ -117,7 +117,7 @@ pub fn main_thread (
         terminal.draw(|frame|{
             let area   = frame.size();
             let buffer = frame.buffer_mut();
-            device.lock().unwrap()
+            device.read().unwrap()
                 .render(buffer, area)
                 .expect("Failed to render content");
         }).expect("Failed to render frame");
@@ -134,7 +134,7 @@ pub fn main_thread (
 /// Spawn thread that listens for user input
 pub fn input_thread (
     exited: &Arc<AtomicBool>,
-    device: &Arc<Mutex<impl Handle + Send + 'static>>
+    device: &Arc<RwLock<impl Handle + Send + Sync + 'static>>
 ) -> JoinHandle<()> {
     let poll = Duration::from_millis(100);
     let exited = exited.clone();
@@ -155,7 +155,7 @@ pub fn input_thread (
                 }) => {
                     exited.store(true, Ordering::Relaxed);
                 },
-                _ => if device.lock().unwrap().handle(&AppEvent::Input(event)).is_err() {
+                _ => if device.write().unwrap().handle(&AppEvent::Input(event)).is_err() {
                     break
                 }
             }
diff --git a/src/core/render.rs b/src/core/render.rs
index 56a3fc1d..4964a421 100644
--- a/src/core/render.rs
+++ b/src/core/render.rs
@@ -62,6 +62,12 @@ impl<T: Render> Render for Arc<Mutex<T>> {
     }
 }
 
+impl<T: Render + Sync> Render for Arc<RwLock<T>> {
+    fn render (&self, b: &mut Buffer, a: Rect) -> Usually<Rect> {
+        self.read().unwrap().render(b, a)
+    }
+}
+
 impl WidgetRef for &dyn Render {
     fn render_ref (&self, area: Rect, buf: &mut Buffer) {
         Render::render(*self, buf, area).expect("Failed to render device.");
diff --git a/src/jack.rs b/src/jack.rs
index ef0a2ebd..1fada643 100644
--- a/src/jack.rs
+++ b/src/jack.rs
@@ -43,7 +43,7 @@ pub use ::_jack::{
 };
 
 /// Just run thing with JACK. Returns the activated client.
-pub fn jack_run <T> (name: &str, app: &Arc<Mutex<T>>) -> Usually<DynamicAsyncClient>
+pub fn jack_run <T: Sync> (name: &str, app: &Arc<RwLock<T>>) -> Usually<DynamicAsyncClient>
     where T: Handle + Process + Send + 'static
 {
     let options = ClientOptions::NO_START_SERVER;
@@ -59,7 +59,7 @@ pub fn jack_run <T> (name: &str, app: &Arc<Mutex<T>>) -> Usually<DynamicAsyncCli
         ClosureProcessHandler::new(Box::new({
             let app = app.clone();
             move|c: &Client, s: &ProcessScope|{
-                app.lock().unwrap().process(c, s)
+                app.write().unwrap().process(c, s)
                 //Control::Continue
             }
         }) as BoxedProcessHandler)
diff --git a/src/main.rs b/src/main.rs
index 9af4db96..f5d8e8a6 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -37,8 +37,8 @@ pub fn main () -> Usually<()> {
     app.quant        = 24;
 
     // Start main loop
-    app.run(Some(|app: Arc<Mutex<App>>|{
-        let mut state = app.lock().unwrap();
+    app.run(Some(|app: Arc<RwLock<App>>|{
+        let mut state = app.write().unwrap();
 
         // Start JACK and setup device graph
         let jack        = jack_run("tek", &app)?;
diff --git a/src/model/phrase.rs b/src/model/phrase.rs
index 258e82b2..d8357a63 100644
--- a/src/model/phrase.rs
+++ b/src/model/phrase.rs
@@ -63,7 +63,7 @@ impl Phrase {
                         _ => {}
                     }
                     LiveEvent::Midi { channel, message }.write(&mut buf).unwrap();
-                    let t = *time as usize;
+                    let t = *time as usize; // FIXME miscalculated, skipping notes
                     output[t].push(buf);
                 }
             }