If you want to go to Oversea to study, you better have IELTS or same level English exam. As it will make your life abit easlier. To study in UK, you have to had at leatest 6.0 or 6.5 to get into UK Sixth form or University (depence what subject)
Be honest, if you have pass you IELTS (or same level exam), when you study in UK or France ... etc. You can spend you time on your study more, otherwise you have to do both at the same time !!! It's all up-to you !!
i think if u r going overseas for further studies...(I assume that u are studying in english-spoken school) it's better for u to 考 IELTS before...
coz it is a prove of your English level, IN CASE u r going to 外國讀音樂學院, AND AT THE SAME TIME no language course is avaliable for u in that school, IELTS is useful when u r trying to find a job or anything that requires a proof of english