diff --git a/src/nodes/node_conf.rs b/src/nodes/node_conf.rs
index 1db8578..686c197 100644
--- a/src/nodes/node_conf.rs
+++ b/src/nodes/node_conf.rs
@@ -354,15 +354,18 @@ impl NodeConfigurator {
             if let Some(modamt) = &mut nparam.modamt {
                 mod_idx  = Some(modamt.0);
                 modamt.1 = v.unwrap_or(0.0);
+                println!("SET NPARAM MOD AMT {:?} {:?} {}", param, mod_idx, modamt.1);
             }
         }
 
-        // Check if the modulation amount was already set, if not, we need
-        // to reconstruct the graph and upload an updated NodeProg.
+
+        // Check if the modulation amount was already set, if not, the caller
+        // needs to reconstruct the graph and upload an updated NodeProg.
         if let Some(_old_modamt) =
             self.param_modamt.get(&param).copied().flatten()
         {
             if v.is_none() {
+                println!("SET NEW NONE MOD AMT {:?}", param);
                 self.param_modamt.insert(param, v);
                 true
 
@@ -371,6 +374,7 @@ impl NodeConfigurator {
                 self.param_modamt.insert(param, v);
 
                 if let Some(mod_idx) = mod_idx {
+                println!("SET UPD MOD AMT {:?} {:?} {:?}", param, mod_idx, modamt);
                     let _ =
                         self.shared.quick_update_prod.push(
                             QuickMessage::ModamtUpdate { mod_idx, modamt });
diff --git a/src/nodes/node_exec.rs b/src/nodes/node_exec.rs
index 646f111..dc30cd3 100644
--- a/src/nodes/node_exec.rs
+++ b/src/nodes/node_exec.rs
@@ -318,6 +318,13 @@ impl NodeExecutor {
     #[inline]
     pub fn get_prog(&self) -> &NodeProg { &self.prog }
 
+    #[inline]
+    fn set_modamt(&mut self, mod_idx: usize, modamt: f32) {
+        if mod_idx < self.prog.modops.len() {
+            self.prog.modops[mod_idx].set_amt(modamt);
+        }
+    }
+
     #[inline]
     fn set_param(&mut self, input_idx: usize, value: f32) {
         let prog = &mut self.prog;
@@ -398,10 +405,8 @@ impl NodeExecutor {
                 QuickMessage::ParamUpdate { input_idx, value } => {
                     self.set_param(input_idx, value);
                 },
-                // TODO: MODAMT
-                // QuickMessage::ModamtUpdate { input_idx, modamt } => {
-                QuickMessage::ModamtUpdate { .. } => {
-                    // assign to NodeProg
+                QuickMessage::ModamtUpdate { mod_idx, modamt } => {
+                    self.set_modamt(mod_idx, modamt);
                 },
                 QuickMessage::SetMonitor { bufs } => {
                     self.monitor_signal_cur_inp_indices = bufs;
@@ -425,41 +430,19 @@ impl NodeExecutor {
 
         let prog_out_fb = prog.out_feedback.input_buffer();
 
-        for op in prog.prog.iter() {
-            let out = op.out_idxlen;
-            let inp = op.in_idxlen;
-            let at  = op.at_idxlen;
+        let nframes = ctx.nframes();
 
+        for op in prog.prog.iter() {
+            let out     = op.out_idxlen;
+            let inp     = op.in_idxlen;
+            let at      = op.at_idxlen;
+            let md      = op.mod_idxlen;
             let ctx_idx = op.idx as usize * 2;
 
-            /* MOD AMOUNT APPLYING PSEUDO CODE:
-
-            for (amt, range, modbuf, outbuf, inpbuf) in
-                prog.mod[mod.0..mod.1].iter()
-            {
-                match range {
-                    ModRange::Bipol => {
-                        for frame in 0..ctx.nframes() {
-                            modbuf.write(frame,
-                                modbuf.read(frame)
-                                * ((outbuf.read(frame) + 1.0) * 0.5)
-                                  .clamp(0.0, 1.0)
-                                + inpbuf.read(frame));
-                        }
-                    },
-                    ModRange::Unipol => {
-                        for frame in 0..ctx.nframes() {
-                            modbuf.write(frame,
-                                modbuf.read(frame)
-                                * outbuf.read(frame).clamp(0.0, 1.0)
-                                + inpbuf.read(frame));
-                        }
-                    },
-                }
+            for modop in prog.modops[md.0..md.1].iter_mut() {
+                modop.process(nframes);
             }
 
-            */
-
             nodes[op.idx as usize]
                 .process(
                     ctx,
@@ -470,7 +453,7 @@ impl NodeExecutor {
                     &mut prog.out[out.0..out.1],
                     &ctx_vals[ctx_idx..ctx_idx + 2]);
 
-            let last_frame_idx = ctx.nframes() - 1;
+            let last_frame_idx = nframes - 1;
             for (pb, out_buf_idx) in
                 prog.out[out.0..out.1].iter()
                     .zip(out.0..out.1)
diff --git a/src/nodes/node_prog.rs b/src/nodes/node_prog.rs
index 578e064..aeb9f5c 100644
--- a/src/nodes/node_prog.rs
+++ b/src/nodes/node_prog.rs
@@ -33,9 +33,11 @@ impl ModOp {
         self.amount = amt;
     }
 
-    pub fn lock(&mut self, inbuf: ProcBuf, outbuf: ProcBuf) {
+    pub fn lock(&mut self, inbuf: ProcBuf, outbuf: ProcBuf) -> ProcBuf {
+        println!("LOCK MA {}", self.amount);
         self.inbuf  = inbuf;
         self.outbuf = outbuf;
+        self.modbuf
     }
 
     pub fn unlock(&mut self) {
@@ -49,11 +51,12 @@ impl ModOp {
         let inbuf  = &mut self.inbuf;
         let outbuf = &mut self.outbuf;
 
+        println!("PROCMA {}", self.amount);
+
         for frame in 0..nframes {
             modbuf.write(frame,
-                modbuf.read(frame)
-                * outbuf.read(frame)
-                + inbuf.read(frame));
+                inbuf.read(frame)
+                + (self.amount * outbuf.read(frame)));
         }
     }
 }
@@ -299,6 +302,7 @@ impl NodeProg {
     pub fn assign_outputs(&mut self) {
         for op in self.prog.iter() {
 
+            println!("ASSIGN OUTPUTS: {}", op);
             // First step is copying the ProcBufs to the `cur_inp` current
             // input buffer vector. It holds the data for smoothed paramter
             // inputs or just constant values since the last smoothing.
@@ -328,7 +332,8 @@ impl NodeProg {
                 input_bufs[io.1] = out_bufs[io.0];
 
                 if let Some(idx) = io.2 {
-                    self.modops[idx].lock(self.inp[io.1], out_bufs[io.0]);
+                    input_bufs[io.1] =
+                        self.modops[idx].lock(self.inp[io.1], out_bufs[io.0]);
                 }
             }
         }