Timbre can be a difficult concept to teach to students. I use this powerpoint and worksheet activity in order to help my students gain a more concrete idea of timbre. This activity takes up an entire class period, but the students really connect with it if you use songs they are familiar with (or fun new ones!) The songs I used are in the "notes" section of the powerpoint on the corresponding slide.
Here is how I use this for my lesson:
First, I go over my timbre "word bank" and explain any words that may be unfamiliar to the students. We go through the powerpoint together. For each artist, I played portions of one of their songs. As we listen, I tell the students to choose at least two words from the word bank and write in under the artist's name. When we are done listening to the song, I click to the slide with the artist's name and timbre words to reveal my choices! Then we compare how many people got the same ones. I also ask students to share if they had any that weren't on my slide for that artist. This opens up a good discussion on what the timbre actually is of each artist's voice/instrument. I've noticed that students have a difficult time differentiating between the song itself and the musical voice quality.
I hope your students enjoy this as much as mine did!