The original Hornbostel/Sachs system had 4 categories:
1. Idiophones - Instruments that vibrate themselves such as a xylophone
2. Membranophones - Instruments that have a vibrating membrane such a as a drum.
3. Chordophones - Instruments with vibrating strings
4. Aerophones - Instruments which incorporate vibration of air.
The answer to the first unknown in the problem is "TIME" while in the second unknown, the answer is "MOTION". Hence, when the traditional visual arts such as painting are inherently static but the artists who created and designed these arts have always found inventive ways and steps of conveying the elements of TIME and MOTION. Sometimes, the artist uses and applies visual clues on the work so that their artwork is static and motionless.
Instead, for color effects, Gothic architects relied on stained-glass windows, which had now become very much larger than in the Romanesque period.
