Now, unlike the harpsichord, which came before it, the piano is a percussion instrument.

MALE PROFESSOR: You see, the harpsichord is actually classified as a string instrument, since pressing a key of a harpsichord causes a tiny quill that’s connected to the key to pluck the strings that are inside the instrument, much the same as a guitar pick plucks the strings of a guitar.

MALE PROFESSOR: But, pressing the keys of a piano causes tiny felt-covered hammers to strike the strings inside the instrument, like drumsticks striking the head of a drum.

请问老师，下面的理解对吗？

这里的much是副词修饰形容词the same，much the same 是形容词后置定语，主语是since从句。

plucks the strings of a guitar  是定语从句修饰a guitar pick。as是比较代词，做省略动词pluck的宾语。

much the same as a guitar pick plucks the strings of a guitar等价于 which is much the same as a guitar pick which plucks the strings of a guitar plucks the string.(the string 必须省略，因为as要充当成分，plucks和since从句重复，可以用does代替，或者直接省略）。这里which指代since从句介绍的harpsichord的发音原理。