Explaining My CD Review Grades

Introduction

My CD Reviews, if you are familiar with them, typically aren't that structured. I usually assign random grades (from 0.0 to 10.0) to every song, add all the numbers up, and divide by the total number of songs to get a grade, which I round to the tenths place. But how do I come up with my grades? Why are some songs 7.7 and others 8.2? The difference between an 8.3 and a 8.4?

Basis and Weight

1. Rhythm - 20% - How's the beat? Do tempo and speed changes affect the song for better or for worse?
2. Instrumentation - 25 % - Are the guitar solos amazing? Percussion fine? Bass line all right? Etc.
3. Vocals - 20% - If the vocals are annoying, the grade will be significantly lowered.
4. Awesomeness - 35% - Looking at the song holistically...how does it rank? It might have some poor qualities, but overall is it good?
5. Comparison to rest of album - Weight varies - This is a criterion that I try not to weigh too heavily. Usually this decides whether a song is a 9.4 or a 9.5. Does this song have any qualities that make itself stand out more than the 9.4 track?

9.7 to 10.0 - Rarely given out; a truly special track
9.0 to 9.6 - High quality, all aspects
8.0 to 8.9 - Weak in only a couple of aspects maximum
7.0 to 7.9 - Average in practically all aspects
6.0 to 6.9 - Below average quality, most aspects
5.0 to 5.9 - Awful, most aspects
0.1 to 4.9 - Very awful
0.0 - Void of sound

* Important Note (Grading): I do most of the calculations in my head to come up with a final grade for a particular song. In certain cases, ones where I find that an album can be exemplified holistically by a certain grade, I will not publish individual song grades. A perfect example is 2009's Merriweather Post Pavillion. While not every song is a 10.0 (if I published grades), an album of this magnitude as a whole represents almost a change in the way a certain of type of music is looked at.

* Important Note (Bias): I have a penchant for lo-fi, noisy rock.