用be able to的形式写作文

　　I was able to play the guitar last year.I am able to play the guitar by ear now.I will be able to perform it on the stage soon.　去年我会弹吉他.现在我能够靠听觉弹吉他.不久我就能登台演奏吉他.但我不会弹吉他唉
我想这样写：2年前我能听一些歌，现在我可以唱一些流行歌曲，以后我能成为一名歌手I was able to sing songs with music two years ago. I am able to sing a lot of popular songs now. I will be able to become a singer later.两年前我能随着乐曲唱歌，现在我可以唱好多流行歌曲，以后我能成为一名歌手。第一句话是sing songs还是sang songs？be able to 后必须用动词原形，因此是 sing，不能用过去式 sang