diff --git a/defaults.ini b/defaults.ini
new file mode 100644
index 0000000..8659fdd
--- /dev/null
+++ b/defaults.ini
@@ -0,0 +1,4 @@
+[DEFAULT]
+Duration = 0.25
+Scale = [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1] # Chromatic
+
diff --git a/ziffers/classes.py b/ziffers/classes.py
index 10acb97..594409f 100644
--- a/ziffers/classes.py
+++ b/ziffers/classes.py
@@ -1,77 +1,204 @@
-from dataclasses import dataclass, asdict
+from dataclasses import dataclass, field
+import operator
+from typing import Any
 
 @dataclass
 class Meta:
+    ''' Abstract class for all Ziffers items'''
+    def update(self, new_values):
+        ''' Update attributes from dict '''
+        for key, value in new_values.items():
+            if hasattr(self, key):
+                setattr(self, key, value)
+
+@dataclass
+class Item(Meta):
+    ''' Class for all Ziffers text based items '''
     text: str
 
 @dataclass
-class DurationChange(Meta):
+class DurationChange(Item):
+    ''' Class for changing duration '''
     dur: float
 
 @dataclass
-class OctaveChange(Meta):
+class OctaveChange(Item):
+    ''' Class for changing octave '''
     oct: int
 
 @dataclass
-class OctaveMod(Meta):
+class OctaveMod(Item):
+    ''' Class for modifying octave '''
     oct: int
 
 @dataclass
-class Event(Meta):
+class Event(Item):
+    ''' Abstract class for events with duration '''
     dur: float = None
 
 @dataclass
 class Pitch(Event):
+    ''' Class for pitch in time '''
     pc: int = None
     dur: float = None
     oct: int = None
 
 @dataclass
 class RandomPitch(Event):
+    ''' Class for random pitch '''
     pc: int = None
 
 @dataclass
-class RandomPercent(Meta):
+class RandomPercent(Item):
+    ''' Class for random percent '''
     percent: float = None
 
 @dataclass
 class Chord(Event):
+    ''' Class for chords '''
     pcs: list[Pitch] = None
     
 @dataclass
 class Function(Event):
+    ''' Class for functions '''
     run: str = None
 
-@dataclass
-class Ziffers:
-    values: list[Event]
-    dict = asdict
-    text: str = None
-    def __post_init__(self):
-        self.text = self.collect_text()
-    def collect_text(self) -> str:
-        return "".join([val.text for val in self.values])
-    def pcs(self) -> list[int]:
-        return [val.pc for val in self.values if type(val) is Pitch]
+class dataclass_property(property): # pylint: disable=invalid-name
+    ''' Hack for dataclass setters '''
+    def __set__(self, __obj: Any, __value: Any) -> None:
+        if isinstance(__value, self.__class__):
+            return None
+        return super().__set__(__obj, __value)
 
 @dataclass
 class Sequence(Meta):
-    values: list[Event]
+    ''' Class for sequences of items'''
+    values: list
+    text: str = None
+    _text: str = field(default=None, init=False, repr=False)
+
+    @dataclass_property
+    def text(self) -> str:
+        return self._text
+
+    @text.setter
+    def text(self, text: str) -> None:
+        self._text = text
+
+    wrapper: str = None
+    _wrapper: str = field(default=None, init=False, repr=False)
+
+    @dataclass_property
+    def wrapper(self) -> str:
+        return self._wrapper
+
+    @wrapper.setter
+    def wrapper(self, wrapper: str) -> None:
+        self._wrapper = wrapper
+        if self.text != None:
+            self.text = self.wrapper[0] + self.text + self.wrapper[1]
+
+    def __post_init__(self):
+        self.text = self.collect_text()
+        if self.text != None and self.wrapper != None:
+            self.text = self.wrapper[0] + self.text + self.wrapper[1]
+
+    def update_values(self, new_values):
+        ''' Update value attributes from dict '''
+        for key, value in new_values.items():
+            for obj in self.values:
+                if key!="text" and hasattr(obj, key):
+                    setattr(obj, key, value)
+    
+    def collect_text(self) -> str:
+        return "".join([val.text for val in self.values])
+    
+    def pcs(self) -> list[int]:
+        return [val.pc for val in self.values if type(val) is Pitch]
+    
+    def durations(self) -> list[float]:
+        return [val.dur for val in self.values if type(val) is Pitch]
+    
+    def pairs(self) -> list[tuple]:
+        return [(val.pc,val.dur) for val in self.values if type(val) is Pitch]
 
 @dataclass
-class Subdivision(Meta):
+class ListSequence(Sequence):
+    ''' Class for Ziffers list sequences '''
+    prefix: dict = None
+    values: list = None
+    def __init__(self):
+        super.__init__()
+        if self.prefix!=None:
+            self.update(self.prefix)
+
+@dataclass
+class Subdivision(Item):
+    ''' Class for subdivisions '''
     values: list[Event]
 
 @dataclass
 class Cyclic(Sequence):
+    ''' Class for cyclic sequences'''
     cycle: int = 0
+    def __post_init__(self):
+        super().__post_init__()
+        # TODO: Do spaced need to be filtered out?
+        self.values = [val for val in self.values if type(val)!=Item]
 
 @dataclass
-class RandomInteger(Meta):
+class RandomInteger(Item):
+    ''' Class for random integer '''
     min: int
     max: int
 
 @dataclass
-class Range(Meta):
+class Range(Item):
+    ''' Class for range '''
     start: int
-    end: int
\ No newline at end of file
+    end: int
+
+ops = {
+    '+' : operator.add,
+    '-' : operator.sub,
+    '*' : operator.mul,
+    '/' : operator.truediv,
+    '%' : operator.mod
+}
+
+@dataclass
+class Operator(Item):
+    ''' Class for math operators '''
+    value: ... = field(init=False, repr=False)   
+    def __post_init__(self):
+        self.value = ops[self.text]
+
+@dataclass
+class ListOperation(Sequence):
+    ''' Class for list operations '''
+    def run(self):
+        pass
+
+@dataclass
+class Operation(Item):
+    ''' Class for lisp-like operations: (+ 1 2 3) etc. '''
+    values: list
+    operator: operator
+
+@dataclass
+class Eval(Sequence):
+    ''' Class for evaluation notation '''
+    result: ... = None
+    def __post_init__(self):
+        super().__post_init__()
+        self.result = eval(self.text)
+
+@dataclass
+class Atom(Item):
+    ''' Class for evaluable atoms'''
+    value: ...
+
+@dataclass
+class Integer(Item):
+    ''' Class for integers '''
+    value: int
\ No newline at end of file
diff --git a/ziffers/common.py b/ziffers/common.py
index 3996faf..c786b4c 100644
--- a/ziffers/common.py
+++ b/ziffers/common.py
@@ -1,2 +1,14 @@
-def flatten(arr) -> list: 
-    return flatten(arr[0]) + (flatten(arr[1:]) if len(arr) > 1 else []) if type(arr) is list else [arr]
\ No newline at end of file
+def flatten(arr) -> list:
+    ''' Flattens array'''
+    return flatten(arr[0]) + (flatten(arr[1:]) if len(arr) > 1 else []) if type(arr) is list else [arr]
+
+def sum_dict(arr) -> dict:
+    ''' Sums array of dicts: [{a:3,b:3},{b:1}] -> {a:3,b:4} '''
+    result = arr[0]
+    for hash in arr[1:]:
+         for key in hash.keys():
+            if key in result:
+                result[key] = result[key] + hash[key]
+            else:
+                result[key] = hash[key]
+    return result
\ No newline at end of file
diff --git a/ziffers/mapper.py b/ziffers/mapper.py
index e5500a2..276fecb 100644
--- a/ziffers/mapper.py
+++ b/ziffers/mapper.py
@@ -1,16 +1,13 @@
 from lark import Transformer
 from .classes import *
-from .common import flatten
+from .common import flatten, sum_dict
 from .defaults import default_durs
+import operator
 
 class ZiffersTransformer(Transformer):
     
-    def root(self, items):
-        return Ziffers(flatten(items))
-
-    def list(self,items):
-        values = flatten(items[0].values)
-        return Sequence(values=values,text="("+"".join([val.text for val in values])+")")
+    def sequence(self,items):
+        return Sequence(values=flatten(items))
 
     def random_integer(self,s):
         val = s[0][1:-1].split(",")
@@ -22,19 +19,12 @@ class ZiffersTransformer(Transformer):
     
     def cycle(self, items):
         values = items[0].values
-        no_spaces = [val for val in values if type(val)!=Meta]
-        return Cyclic(values=no_spaces,text="<"+"".join([val.text for val in values])+">")
+        return Cyclic(values=values, wrapper="<>")
 
     def pc(self, s):
         if(len(s)>1):
             # Collect&sum prefixes from any order: _qee^s4 etc.
-            result = s[0]
-            for hash in s[1:]:
-                for key in hash.keys():
-                    if key in result:
-                        result[key] = result[key] + hash[key]
-                    else:
-                        result[key] = hash[key]            
+            result = sum_dict(s)
             return Pitch(**result)
         else:
             val = s[0]
@@ -89,7 +79,7 @@ class ZiffersTransformer(Transformer):
         key = s[0]
         val = default_durs[key]
         dots = len(s)-1
-        if(dots>1):
+        if(dots>0):
             val = val * (2.0-(1.0/(2*dots)))
         return [key+"."*dots,val]
 
@@ -105,7 +95,7 @@ class ZiffersTransformer(Transformer):
         return chardur
 
     def WS(self,s):
-        return Meta(text=s[0])
+        return Item(text=s[0])
 
     def subdivision(self,items):
         values = flatten(items[0])
@@ -113,3 +103,50 @@ class ZiffersTransformer(Transformer):
 
     def subitems(self,s):
         return s
+
+    # Eval rules
+
+    def eval(self,s):
+        val = s[0]
+        return Eval(values=val,wrapper="{}")
+
+    def operation(self,s):
+        return s
+
+    def atom(self,s):
+        val = s[0].value
+        return Atom(value=val,text=val)
+
+    # List rules
+
+    def list(self,items):
+        if len(items)>1:
+            prefixes = sum_dict(items[0:-1])
+            seq = items[-1]
+            seq.wrapper = "()"
+            seq.text = prefixes["text"] + seq.text
+            seq.update_values(prefixes)
+            return seq
+        else:
+            seq = items[0]
+            seq.wrapper = "()"
+            return seq
+    
+    def SIGNED_NUMBER(self, s):
+        val = s.value
+        return Integer(text=val,value=int(val))
+
+    def lisp_operation(self,s):
+        op = s[0]
+        values = s[1:]
+        return Operation(operator=op,values=values,text="(+"+"".join([v.text for v in values])+")")
+
+    def operator(self,s):
+        val = s[0].value
+        return Operator(text=val)
+
+    def list_items(self,s):
+        return Sequence(values=s)
+
+    def list_op(self,s):
+        return ListOperation(values=s)
\ No newline at end of file
diff --git a/ziffers/parser.py b/ziffers/parser.py
index 4862b59..83f801a 100644
--- a/ziffers/parser.py
+++ b/ziffers/parser.py
@@ -6,7 +6,7 @@ from lark import Lark
 grammar_path = Path(__file__).parent
 grammar = grammar_path / "ziffers.lark"
 
-ziffers_parser = Lark.open(grammar, rel_to=__file__, start='value', parser='lalr', transformer=ZiffersTransformer())
+ziffers_parser = Lark.open(grammar, rel_to=__file__, start='root', parser='lalr', transformer=ZiffersTransformer())
 
 def parse_expression(expr):
     return ziffers_parser.parse(expr)
\ No newline at end of file
diff --git a/ziffers/ziffers.lark b/ziffers/ziffers.lark
index 106f7fa..574308a 100644
--- a/ziffers/ziffers.lark
+++ b/ziffers/ziffers.lark
@@ -1,29 +1,59 @@
+    // Root for the rules    
+    ?root: sequence  
+    sequence: (pc | dur_change | oct_mod | oct_change | WS | chord | cycle | random_integer | random_pitch | random_percent | range | list | lisp_operation | list_op | subdivision | eval)*
     
-    ?value: root      
-    root: (pc | dur_change | oct_mod | oct_change | WS | chord | cycle | random_integer | random_pitch | random_percent | range | list | subdivision)*
-    list: "(" root ")"
-    random_integer: /\(-?[0-9]+,-?[0-9]+\)/
-    range: /-?[0-9]\.\.-?[0-9]/
-    cycle: "<" root ">"
+    // Pitch classes
     pc: prefix* pitch
-    pitch: /-?[0-9TE]/
-    random_pitch: "?"
-    random_percent: "%"
     prefix: (octave | duration_chars | escaped_decimal | escaped_octave)
-    oct_change: escaped_octave WS
-    escaped_octave: /<-?[0-9]>/
-    oct_mod: octave WS
-    octave: /[_^]+/
-    chord: pc pc+
+    pitch: /-?[0-9TE]/
     escaped_decimal: "<" decimal ">"
-    dur_change: (duration_chars | decimal) WS
+    escaped_octave: /<-?[0-9]>/
+    octave: /[_^]+/
+   
+    // Chords
+    chord: pc pc+
+  
+    // List
+    list: prefix* "(" sequence ")"
+
+    // Right recursive list operation
+    list_op: list (operator (list | number))+
+    operator: /([\+\-\*\/%]|<<|>>)/
+    ?number: SIGNED_NUMBER
+
+    // Lisp like list operation
+    lisp_operation:  "(" operator WS sequence ")"
+ 
+    // Durations
     duration_chars: dotted_dur+
     dotted_dur: dchar dot*
     decimal: /-?[0-9]+\.[0-9]+/
     dchar: /[mklpdcwyhnqaefsxtgujzo]/
     dot: "."
-    subitems: (pc | WS | chord | cycle | subdivision)*
-    subdivision: "[" subitems "]"
 
+    // Subdivision
+    subdivision: "[" subitems "]"
+    subitems: (pc | WS | chord | cycle | subdivision)*
+
+    // Control characters modifying future events
+    oct_mod: octave WS
+    oct_change: escaped_octave WS
+    dur_change: (duration_chars | decimal) WS
+
+    // Generative rules
+    random_integer: /\(-?[0-9]+,-?[0-9]+\)/
+    range: /-?[0-9]\.\.-?[0-9]/
+    cycle: "<" sequence ">"
+    random_pitch: "?"
+    random_percent: "%"
+
+    // Rules for evaluating clauses inside {}
+    // TODO: Support for parenthesis?
+    eval: "{" operation "}"
+    operation: atom (operator atom)+  
+    atom: (SIGNED_NUMBER | DECIMAL | random_integer)
+
+    %import common.NUMBER
     %import common.SIGNED_NUMBER
+    %import common.DECIMAL
     %import common.WS
\ No newline at end of file