I used The Story of the Orchestra by Robert Levine as our spine. This book is organized into two main sections, the composers and the instruments. We focused on the second part this time, the orchestra instruments. The book includes an audio CD and most pages prompt you to play a certain track. We listened to small samples of music that highlighted each of the instruments from the orchestra.
We enjoyed a few picture books were available at our local library:
The Story of the Incredible Orchestra by Bruce Koscielniak
Mole Music by David McPhail
Animal Music by Harriet Zieffert
Little Rat Makes Music by Monika Bang-Campbell
The Composer is Dead by Lemony Snicket
We listened to "Elmo and the Orchestra", found in the CD section at our library. I had picked up this one mostly for Celeste, but we all enjoyed it! I was surprised how it included works by Bach, Beethoven, Mozart, and Tchaikovsky. It was really well done and tied in perfectly with our main book.
We also found at our library (we love our library!) a Reading Rainbow DVD with a theme of music and orchestra. It is called "Music, Music, Everywhere". It was also a perfect addition to our study.
This time, we didn't put together a lapbook or notebook. I did find a few sites that might interest you if you are planning on doing this type of study.
Orchestra Lapbook Unit
Classical Music Lapbook
Instruments of the Orchestra (quick matching game - sound to its instrument)
Young Person's Guide to the Orchestra (a great game!)
Classics for Kids (games, radio show, and more...this is another wonderful site)
Learning about the orchestra at our house was just an introduction, but I know we will get back to this study in the future and take advantage of all the wonderful *free* resources that are available on the internet!