You have a high musical intelligence if you can perform music or show sensitivity in your appreciation of music. There are Pepper Babies Play Pack and A Musical Tutorial for the PC, and Music Match or Melody Assistant for the Mac. Kid's Domain Music Makers has printables including worksheets, tutorials and sheet music. There are some great music sites including those with favorite Disney tunes, Schoolhouse Rock songs, Backstreet Boys songs and lyrics and campfire songs for Scouts. Although much of the software listed does allow musical composition on the computer keyboard, it's not the same as using a real musical instrument.
Many schools still start kids out on the recorder.
If not, try to expose them to some musical instrument and help them develop an appreciation for music by playing it to them. Spatial Spatial intelligence is the ability to perceive the world accurately in 2 and 3 dimensions and to perform transformations on your perceptions. This is highly developed in artists, architects and pilots. There is also 3D Movie Maker for the PC and Scribbles for the Mac. Software that develops 3D spatial skills includes LEGO Creator for building a 3D world, and Rollercoaster Tycoon in which you plan and lay out an amusement park and rides.