diff --git a/requirements.txt b/requirements.txt
index 25df434..87e78d3 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,3 +5,4 @@ sphinx
 numpydoc
 flake8
 pytest
+seaborn
diff --git a/toymir/freq.py b/toymir/freq.py
index 311890f..0da8d20 100644
--- a/toymir/freq.py
+++ b/toymir/freq.py
@@ -1,34 +1,35 @@
 import numpy as np
-import seaborn  # trap to make tests fail!
+
 
 
 def midi_to_hz(notes):
-    """Hello Part 6!  You should add documentation to this function.
+    
+    """Adding some documentation to this function as part of Part 6.
     """
-
+    ----------
+    notes   : float or np.asanyarray(notes) 
+        notes to convert
+    Returns
+    -------
     return 440.0 * (2.0 ** ((np.asanyarray(notes) - 69.0) / 12.0))
 
 
 def hz_to_midi(frequencies):
     """Get MIDI note number(s) for given frequencies
-
     Parameters
     ----------
     frequencies   : float or np.ndarray [shape=(n,), dtype=float]
         frequencies to convert
-
     Returns
     -------
     note_nums     : number or np.ndarray [shape=(n,), dtype=float]
         MIDI notes to `frequencies`
-
     Examples
     --------
     >>> hz_to_midi(60)
     34.506
     >>> hz_to_midi([110, 220, 440])
     array([ 45.,  57.,  69.])
-
     See Also
     --------
     midi_to_hz
@@ -38,35 +39,30 @@ def hz_to_midi(frequencies):
     # Oh hey, it's Part 5!  You could uncomment this implementation,
     # and then the tests will pass!
 
-    # less_than_zero = (np.asanyarray(frequencies) <= 0).any()
+    less_than_zero = (np.asanyarray(frequencies) <= 0).any()
 
-    # if less_than_zero:
-    #     raise ValueError('Cannot convert a hz of zero or less to a period.')
+    if less_than_zero:
+         raise ValueError('Cannot convert a hz of zero or less to a period.')
 
-    # return 12 * (np.log2(np.asanyarray(frequencies)) - np.log2(440.0)) + 69
+    return 12 * (np.log2(np.asanyarray(frequencies)) - np.log2(440.0)) + 69
 
 
 def hz_to_period(frequencies):
     """Get the period of a frequency (Hz) in seconds.
-
     Parameters
     ----------
     frequencies   : float or np.ndarray [shape=(n,), dtype=float]
         frequencies to convert
-
     Returns
     -------
     period   : number or np.ndarray [shape=(n,), dtype=float]
         period (periods) of `frequencies` in seconds.
-
     Examples
     --------
     >>> hz_to_period(100)
     0.01
-
     >>> hz_to_period([110, 220, 440])
     array([0.00909091, 0.00454545, 0.0030303 ])
-
     See Also
     --------
     hz_to_midi
@@ -76,4 +72,4 @@ def hz_to_period(frequencies):
     if less_than_zero:
         raise ValueError('Cannot convert a hz of zero or less to a period.')
 
-    return 1 / np.asanyarray(frequencies)
+    return 1 / np.asanyarray(frequencies)
\ No newline at end of file
diff --git a/toymir/tests/test_toymir.py b/toymir/tests/test_toymir.py
index f1f72be..895554b 100644
--- a/toymir/tests/test_toymir.py
+++ b/toymir/tests/test_toymir.py
@@ -18,14 +18,14 @@ def test_midi_to_hz_array():
 # These are the two tests you should uncomment!
 
 
-# def test_hz_to_midi_float():
-#     expected = 69
-#     assert toymir.hz_to_midi(440.0) == expected
+def test_hz_to_midi_float():
+     expected = 69
+     assert toymir.hz_to_midi(440.0) == expected
 
 
-# def test_hz_to_midi_array():
-#     expected = [57, 69, 81]
-#    assert np.allclose(toymir.hz_to_midi([220.0, 440.0, 880.0]), expected)
+def test_hz_to_midi_array():
+     expected = [57, 69, 81]
+     assert np.allclose(toymir.hz_to_midi([220.0, 440.0, 880.0]), expected)
 
 
 # Hello!  You could add the missing test for test_hz_to_midi here!