diff --git a/bin/curvecalc b/bin/curvecalc
--- a/bin/curvecalc
+++ b/bin/curvecalc
@@ -172,15 +172,27 @@ class Main(object):
             self.makeSubterm(newname, withCurve=wc)
         dialog.hide()
 
-    def currentSong(self):
-        with self.graph.currentState() as current:
+    def currentSong(self, current=None):
+        def fin(current):
             return current.value(self.session, L9['currentSong'])
+        if current is None:
+            with self.graph.currentState() as current:
+                return fin(current)
+        else:
+            return fin(current)
 
-    def songSubtermsContext(self):
-        return self.currentSong()
+    def songSubtermsContext(self, current=None):
+        return self.currentSong(current=current)
 
     def makeSubterm(self, newname, withCurve=False, expr=None, sub=None):
-        uri = self.currentSong() + "/sub/%f" % time.time()
+        with self.graph.currentState() as current:
+            song = self.currentSong(current=current)
+            for i in range(1000):
+                uri = song + "/subterm/%d" % i
+                if (uri, None, None) not in current:
+                    break
+            else:
+                raise ValueError("can't pick a name for the new subterm")
 
         ctx = self.songSubtermsContext()
         quads = [
diff --git a/light9/curvecalc/curvecalc.glade b/light9/curvecalc/curvecalc.glade
--- a/light9/curvecalc/curvecalc.glade
+++ b/light9/curvecalc/curvecalc.glade
@@ -526,7 +526,7 @@
                         </child>
                       </object>
                       <packing>
-                        <property name="expand">False</property>
+                        <property name="expand">True</property>
                         <property name="fill">True</property>
                         <property name="position">0</property>
                       </packing>
@@ -535,11 +535,12 @@
                       <object class="GtkLabel" id="newSubZone">
                         <property name="visible">True</property>
                         <property name="can_focus">False</property>
+                        <property name="ypad">18</property>
                         <property name="label" translatable="yes">Drop new sub here</property>
                         <signal name="drag-data-received" handler="onDragDataInNewSubZone" swapped="no"/>
                       </object>
                       <packing>
-                        <property name="expand">True</property>
+                        <property name="expand">False</property>
                         <property name="fill">True</property>
                         <property name="position">1</property>
                       </packing>
diff --git a/light9/curvecalc/subterm.py b/light9/curvecalc/subterm.py
--- a/light9/curvecalc/subterm.py
+++ b/light9/curvecalc/subterm.py
@@ -100,6 +100,8 @@ class Subterm(object):
             else:
                 # otherwise, return our submaster multiplied by the value 
                 # returned
+                if subexpr_eval == 0:
+                    return Submaster.Submaster("zero", {})
                 subUri = current.value(self.uri, L9['sub'])
                 sub = self.submasters.get_sub_by_uri(subUri)
                 return sub * subexpr_eval
@@ -113,6 +115,7 @@ class Subterm(object):
 
         expr = current.value(self.uri, L9['expression'])
         
+        expr = current.value(self.uri, L9['expression'])
         if not expr:
             dispatcher.send("expr_error", sender=self.uri, exc="no expr, using 0")
             return 0
diff --git a/light9/curvecalc/subtermview.py b/light9/curvecalc/subtermview.py
--- a/light9/curvecalc/subtermview.py
+++ b/light9/curvecalc/subtermview.py
@@ -35,14 +35,13 @@ class Subexprview(object):
         
     def set_expression_from_graph(self):
         e = str(self.graph.value(self.ownerSubterm, L9['expression']))
-        print "was going to set to %r" % e
+        print "from graph, set to %r" % e
 
         if e != self.entryBuffer.get_text():
             self.entryBuffer.set_text(e, len(e))
             
     def entry_changed(self, *args):
         log.info("want to patch to %r", self.entryBuffer.get_text())
-        return
         self.graph.patchObject(self.saveContext,
                                self.ownerSubterm,
                                L9['expression'],