This lesson is most effective when the students can see the instruments demonstrated and see how they work. I am a clarinetist, can play oboe relatively well, and can play saxophone and flute better than middle schoolers (lol), so those were easy for me to demonstrate. I also was able to give some demonstration on the trumpet and trombone, and later on violin (which I can play) and a little on cello. (This lesson was created and presented during my internship at an elementary school).
In this lesson students are introduced to various types of instruments, how they produce sound, and what instrument family they belong to. The word timbre is introduced, and descriptive words are used for the instruments. A flute could be described as clear, light, airy. A tuba might be described as fat, round, heavy, and so on. After the presentation of instruments students sing a song about instruments, using motions to aid in remembering (and makes it more fun!). I have provided a worksheet that I used to help students test their knowledge of the instrument timbres. This can also double as an assessment.