添加+时，URL重写规则失败匹配

Question

以下重写规则适用于网址：

https://www.example.com/muziek/liedjes-start+meeting/modern

但是通过此网址，我得到了HTTP Error 404.0 - Not Found https://www.example.com/muziek/liedjes-start+meeting/rhythm+and+blues

  <rule name="song overview occasion + genre">
    <match url="^(muziek/liedjes|music/songs)-([a-zA-Z-+]+)/([a-zA-Z-+]+)$"/>
    <action type="Rewrite" url="songs.aspx?category={R:2}&amp;genre={R:3}" appendQueryString="true"/>
  </rule>

所以在第二个URL中，重写不起作用......为什么不呢？