P7-1

Hint
"Rock band!"

Solutions

 * Write any four sound-producing objects.

Notes:
 * It can be the same object four times.
 * They don't have musical instruments. Writing four Fire alarms, CD Players or four Singers will also win.
 * They objects don't have to be give to the people to hold (for some larger instruments - like the Harpsichord this is not possible).