Musical instruments and the skill required to play them are both aspects of Man attempting to be close to the Divine. Ways of self-expression (for example, playing a musical instrument) are offerings of our own creativity and are spiritual acts. In dreams, we have access to vibrations and rhythms not always accessible in waking life.
Psychological / Emotional Perspective:
Sound produced by musical instruments is evocative of emotion. The symbolism of the instrument itself appearing may allow us to come to terms with that emotion in a slightly more objective way. Not being able to play a particular instrument suggests we do not have access to that emotion.
Everyday Material Aspects:
Musical instruments in a dream often stand for our skills and abilities in communication. Wind instruments tend to suggest the intellect, whereas percussion instruments suggest the basic rhythm of life. Stringed instruments calm the nervous system, so when these appear in dreams we are able to act accordingly in waking life.
Consult the entries for Drum, Flute and Organ for further information.