The pictures of instruments can be identified as a BASS DRUM, COWBELL, GUITAR, KAZOO, SAXOPHONE, TAMBOURINE, TROMBONE, and TUBA. The pictures were given in alphabetical order to make it slightly easier to identify missing instruments.
Each of these instrument names contains a different number of letters (with the exception of bass drum, which has the same number of letters as trombone, but does include a space). This allows the names to be put in the grid in exactly one way.
Reading down the only complete column, we see the answer, MUSIC BOX.