diff --git a/abjad/tools/indicatortools/Dynamic.py b/abjad/tools/indicatortools/Dynamic.py
index fc4d5837531..7e100684e23 100644
--- a/abjad/tools/indicatortools/Dynamic.py
+++ b/abjad/tools/indicatortools/Dynamic.py
@@ -53,6 +53,11 @@ class Dynamic(AbjadValueObject):
 
     ### CLASS VARIABLES ###
 
+    __slots__ = (
+        '_default_scope',
+        '_name',
+        )
+
     _format_slot = 'right'
 
     _composite_dynamic_name_to_steady_state_dynamic_name = {
diff --git a/abjad/tools/indicatortools/KeySignature.py b/abjad/tools/indicatortools/KeySignature.py
index 92e7c0c1e62..1b71c82cd85 100644
--- a/abjad/tools/indicatortools/KeySignature.py
+++ b/abjad/tools/indicatortools/KeySignature.py
@@ -27,6 +27,12 @@ class KeySignature(AbjadValueObject):
 
     ### CLASS VARIABLES ###
 
+    __slots__ = (
+        '_default_scope',
+        '_mode',
+        '_tonic',
+        )
+
     _format_slot = 'opening'
 
     ### INITIALIZER ###
diff --git a/abjad/tools/mathtools/Infinity.py b/abjad/tools/mathtools/Infinity.py
index a2d744568a8..7eaab772f9b 100644
--- a/abjad/tools/mathtools/Infinity.py
+++ b/abjad/tools/mathtools/Infinity.py
@@ -35,6 +35,12 @@ class Infinity(AbjadObject):
     global Abjad namespace.
     '''
 
+    ### CLASS VARIABLES ###
+
+    __slots__ = (
+        '_value',
+        )
+
     ### INTIALIZER ###
 
     def __init__(self):
@@ -111,4 +117,4 @@ def _storage_format_specification(self):
             storage_format_pieces=(
                 type(self).__name__,
                 ),
-            )
+            )
\ No newline at end of file
diff --git a/abjad/tools/pitchtools/NamedIntervalClass.py b/abjad/tools/pitchtools/NamedIntervalClass.py
index 069e23c389e..e08158c7752 100644
--- a/abjad/tools/pitchtools/NamedIntervalClass.py
+++ b/abjad/tools/pitchtools/NamedIntervalClass.py
@@ -15,6 +15,11 @@ class NamedIntervalClass(IntervalClass):
 
     ### CLASS VARIABLES ###
 
+    __slots__ = (
+        '_number',
+        '_quality_string',
+        )
+
     _acceptable_quality_strings = (
         'perfect',
         'major',
@@ -54,7 +59,6 @@ class NamedIntervalClass(IntervalClass):
 
     def __init__(self, *args):
         from abjad.tools import pitchtools
-        from abjad.tools import sequencetools
         if len(args) == 1 and \
             isinstance(args[0], (pitchtools.NamedInterval,
                 pitchtools.NamedIntervalClass)):
diff --git a/abjad/tools/pitchtools/NamedInversionEquivalentIntervalClass.py b/abjad/tools/pitchtools/NamedInversionEquivalentIntervalClass.py
index 63e801bde4c..89dbe7f5677 100644
--- a/abjad/tools/pitchtools/NamedInversionEquivalentIntervalClass.py
+++ b/abjad/tools/pitchtools/NamedInversionEquivalentIntervalClass.py
@@ -14,6 +14,13 @@ class NamedInversionEquivalentIntervalClass(NamedIntervalClass):
     Inversion-equivalent diatonic interval-classes are immutable.
     '''
 
+    ### CLASS VARIABLES ###
+
+    __slots__ = (
+        '_number',
+        '_quality_string',
+        )
+
     ### INITIALIZER ###
 
     def __init__(self, *args):
diff --git a/abjad/tools/timespantools/OffsetTimespanTimeRelation.py b/abjad/tools/timespantools/OffsetTimespanTimeRelation.py
index c6f45dc8d5a..b276f251bbc 100644
--- a/abjad/tools/timespantools/OffsetTimespanTimeRelation.py
+++ b/abjad/tools/timespantools/OffsetTimespanTimeRelation.py
@@ -38,6 +38,13 @@ class OffsetTimespanTimeRelation(TimeRelation):
     Offset / timespan time relations are immutable.
     '''
 
+    ### CLASS VARIABLES ###
+
+    __slots__ = (
+        '_offset',
+        '_timespan',
+        )
+
     ### INITIALIZER ###
 
     def __init__(self, inequality=None, timespan=None, offset=None):
@@ -193,4 +200,4 @@ def timespan(self):
 
         Returns timespan or none.
         '''
-        return self._timespan
+        return self._timespan
\ No newline at end of file
diff --git a/abjad/tools/timespantools/TimeRelation.py b/abjad/tools/timespantools/TimeRelation.py
index f08fb31d5d2..4aabcc0dcf6 100644
--- a/abjad/tools/timespantools/TimeRelation.py
+++ b/abjad/tools/timespantools/TimeRelation.py
@@ -9,14 +9,20 @@ class TimeRelation(AbjadObject):
     Time relations are immutable.
     '''
 
+    ### CLASS VARIABLES ###
+
+    __slots__ = (
+        '_inequality',
+        )
+
     ### INITIALIZER ###
 
     def __init__(self, inequality=None):
         from abjad.tools import timespantools
-        default_inequality = timespantools.CompoundInequality([
-            'timespan_1.start_offset < timespan_2.start_offset',
-            ])
-        inequality = inequality or default_inequality
+        if not inequality:
+            inequality = timespantools.CompoundInequality([
+                'timespan_1.start_offset < timespan_2.start_offset',
+                ])
         assert isinstance(
             inequality, timespantools.CompoundInequality), repr(inequality)
         self._inequality = inequality
diff --git a/abjad/tools/timespantools/TimespanTimespanTimeRelation.py b/abjad/tools/timespantools/TimespanTimespanTimeRelation.py
index a42e483ee86..194d6a3de69 100644
--- a/abjad/tools/timespantools/TimespanTimespanTimeRelation.py
+++ b/abjad/tools/timespantools/TimespanTimespanTimeRelation.py
@@ -145,10 +145,16 @@ class TimespanTimespanTimeRelation(TimeRelation):
     Timespan / timespan time relations are immutable.
     '''
 
+    ### CLASS VARIABLES ###
+
+    __slots__ = (
+        '_timespan_1',
+        '_timespan_2',
+        )
+
     ### INITIALIZER ###
 
     def __init__(self, inequality=None, timespan_1=None, timespan_2=None):
-        from abjad.tools import timespantools
         TimeRelation.__init__(self, inequality=inequality)
         self._timespan_1 = timespan_1
         self._timespan_2 = timespan_2
@@ -494,4 +500,4 @@ def get_offset_indices(
         elif 0 < len(result):
             message = 'inequality evaluates to disjunct range: {!r}.'
             message = message.format(result)
-            raise Exception(message)
+            raise Exception(message)
\ No newline at end of file