先還原一下句子結(jié)構(gòu).
在第一句中,what 代替的部分是：visual artists (like painters-此為插入語,可以先忽略）want to teach
在這句話中：visual artists what to teach這句語是不完整的,缺少了主語,完整句應該是that is visual artists what to teach.所以用what在這里相當于that is.因此這個句子也可以拆分成這樣：
That is visual artists like painters want to teach,and that is easy to make.
在第二句中,that代替的部分是：I am intersting in piano
在這句話中：I am intersting in piano已經(jīng)是完整句,不缺任何成分,所以that代替的就是一個完整句,而不充當從句中任何語法成分.而在主語.is the secret of my success中,that引導的從句充當主語成分,所以這個也叫that引導的主語從句