The Electromusic Exhibit is terrific. If you have any interest in this type of music, be sure to book it while in Paris. We spent the afternoon there today and loved it. Lots of interesting visual experiences and everyone gets headphones with a jack you can plug into ports to hear the various exhibits. If you go, the first row of stuff to see is basically a history timeline of this music and that part is all in French and the people ahead of you will read every word, so there is this huge long wait and slow line along that display --- skip it and go see and hear stuff -- you can always read up on the history. The major sections like exhibits at museums are done in French and English, so you will be able to read about the different genre etc in English. And of course some of the video is in English with French subtitles as much of this music is American or British in origin.
If you have never seen the Philharmonie, reserve some time to just look at this wonderful. building. You can go up on the roof for a great view as well - for free.