How can one guitar string produce different notes?
同一根吉他弦，怎么弹出不同的音？
弹吉他时，同一根弦能发出不同的音。
When a guitar is played, the same string can produce different notes.
看演奏者的手，按弦的位置一直在变。
Look at the player's hand: the position where the string is pressed keeps changing.
他们没有剪短琴弦，为什么还能让音变高？
They have not cut the string shorter, so how can they still make the note higher?
秘密在于：整根弦还那么长，可以自由振动的部分却变了。
The secret is that the whole string is still just as long, but the part that can vibrate freely has changed.
振动就是来回运动，振动得越快，发出的音通常越高。
Vibration is back-and-forth motion; faster vibration generally produces a higher note.
这里说的是音高，不是声音有多大。
This means the pitch of the sound, rather than how loud it is.
在更靠近吉他主体的品位按弦，会让可以自由振动的部分变短。
Pressing the string at a fret closer to the guitar's body shortens the part that can vibrate freely.
品位就是琴颈上用来按出不同音的位置。
Fret positions are places along the guitar's neck used to produce different notes by pressing the string.
比较同一根弦，在松紧差不多时，振动的部分越短，音就越高。
For the same string, with its tension almost unchanged, a shorter vibrating section gives a higher note.
不过，弦的粗细和松紧也会影响音高。
However, a string's thickness and tension also affect its pitch.
所以，比较不同的弦时，不能只看长度。
When comparing different strings, therefore, length alone is not enough.
手指看起来只是在按弦，其实也在为同一根弦选择不同的振动长度。
The fingers seem merely to press the string, but they also choose different vibrating lengths for that same string.
