I know! It was a hard test!  Consider it practice...although, if you did great, consider it an accomplishment:)  Homework today is to find the answers to the problems you missed on the test, by searching your textbook, and to make OK answers better answers.This is to be written down.  Use extra paper. 

Homework also is to work on musical instruments:

1. Finding and choosing an instrument to make yourself.  Not too easy; not too hard.  Consider the limitations of your time, tools, and materials.  Ask your mom whether she thinks it is a reasonable choice. Ask your dad too, and getting help is fine; anything dangerous like using power tool, have adult supervision.
2. Getting the materials
3. Building it.
4. Learn to play a simple song.
5. As you can see, this is a medium-sized project, so don't put it off.

Here are some resources (see also youtube, pinterest, and Google "homemade musical instruments") and from Instructables, here is a picture-list to browse from http://www.instructables.com/howto/musical+instruments/ -- LOTSSsss of ideas!

Inventing Homemade instruments with math and measurement - which has pages you can link to
Very precise instructions, including measurements, which is essential to getting the pitches right.

Melodic Tube Drums

Pan Pipes

Didgeritubes

Glockenspiel

Water Bottle Xylophone

Fraction Tubes

  These are projects with directions and measurements, but you can also play them virtually online.  Fun.