Article
OpenStax

Open Stax: Catherine Schmidt Jones: Scales That Aren't Major or Minor

For Students 9th - 10th
As the title suggests, this site defines and gives examples of various other types of scales including chromatic, whole tone, blues scales and more.
Unit Plan
Open Curriculum

Open Curriculum: Scales That Are Not Major or Minor

For Teachers 9th - 10th
To explain the various musical scales that cannot be classified as major or minor such as chromatic, whole-tone, pentatonic, blues, and scales from non-Western music
Article
Other

Music Theory First Aid for Struggling Students

For Students 9th - 10th
This site provides music theory information on such topics as rhythm, intervals, scales, chords, etc. Also, there is a fine section which describes the basic concepts of form and structure.
Article
OpenStax

Open Stax: Catherine Schmidt Jones: Half Steps and Whole Steps

For Students 9th - 10th
Take a look at the two intervals of the half step and whole step and how they make up the chromatic and whole tone scales. This page includes a couple of self checking problems to test your knowledge.
Website
Music Theory

Music theory.net

For Students 9th - 10th
An online beginning music theory and ear training site. This site is for students to use at home to reinforce what they learn in class.
Graphic
Other

Boerger: French Horn Fingerings

For Students 9th - 10th
A basic fingering chart for all notes in a chromatic scale.