Final answer:
To differentiate between two unidentified musical instruments based on pitch without hearing them, examine their size, with smaller instruments producing higher pitches and larger ones producing lower pitches. You can also consider the resonating chamber size and string length.
Step-by-step explanation:
If you observe two musical instruments that you cannot identify, and you need to determine which one plays high-pitched sounds and which one plays low-pitched sounds without hearing them, you can often tell by their physical characteristics. Typically, smaller instruments are likely to produce higher-pitched notes, while larger instruments tend to produce lower-pitched notes. This is due to the sound waves that each instrument produces. The larger the instrument, the longer the sound wave and the lower the pitch will be. Conversely, the smaller the instrument, the shorter the sound wave and the higher the pitch.
For example, if one instrument is large, like a tuba, and the other is small, like a flute, you can deduce that the tuba will produce the low-pitched sounds and the flute will produce the high-pitched sounds. It's also helpful to look at the size of the resonating chamber and the length of the strings (if the instrument has strings), as these can also impact the pitch.