adding mfcc

Table_of_Contents.ipynb

 {
  "metadata": {
   "name": "",
-  "signature": "sha256:c2091c83f372205a4ebcdce326aec16d3effc143ec24d63e1026df692ec4f383"
+  "signature": "sha256:ba6914e86f65c927f3b3e5e0880193335eae98cda6317da50d32966ac28f77c1"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -66,19 +66,17 @@
      "level": 2,
      "metadata": {},
      "source": [
-      "Feature Extraction (work in progress)"
+      "Spectral Feature Extraction and Classification"
      ]
     },
     {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "1.  [Feature Extraction](notebooks/feature_extraction.ipynb)\n",
       "1.  [Spectral Features](notebooks/spectral_features.ipynb)\n",
       "1.  [Tonal Descriptors: Pitch and Chroma](notebooks/)\n",
-      "1.  [Beat Tracking](notebooks/beat_tracking.ipynb)\n",
-      "1.  [Tempo Estimation](notebooks/tempo_estimation.ipynb)\n",
       "1.  [Mel-Frequency Ceptral Coefficients](notebooks/mfcc.ipynb)\n",
+      "1.  [K-Nearest Neighbor](notebooks/knn.ipynb)\n",
       "1.  [Exercise: Instrument Classification using K-NN](exercises/knn_instrument_classification.ipynb)"
      ]
     },
@@ -87,14 +85,16 @@
      "level": 2,
      "metadata": {},
      "source": [
-      "Machine Learning (work in progress)"
+      "More (work in progress)"
      ]
     },
     {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
-      "1.  [K-Nearest Neighbor](notebooks/knn.ipynb)\n",
+      "1.  [Feature Extraction](notebooks/feature_extraction.ipynb)\n",
+      "1.  [Beat Tracking](notebooks/beat_tracking.ipynb)\n",
+      "1.  [Tempo Estimation](notebooks/tempo_estimation.ipynb)\n",
       "1.  [K-Means Clustering](notebooks/kmeans.ipynb)\n",
       "1.  [Nonnegative Matrix Factorization](notebooks/nmf.ipynb)\n",
       "1.  [Cross Validation](notebooks/cross_validation.ipynb)\n",