I'm not the biggest fan of Late Night and still after all these years have not tested everything this EP has to offer... Pardon me if I'm asking dumb questions, but can teenagers form a band? I've noticed that an adult sim with music skills can ask another sim to form a band with them, but even if my teenager sim is an excellent pianist, I haven't seen the same option for her. 

If the game itself doesn't allow teens to form a band (which is weird and stupid), is there a mod to make it possible? I'd really love them to form a garage band from so many movies...

Also, a side note, it's kind of ridiculous that you can't have a singer in your band... 

No, teens cannot form a band without the help of a mod. Might this be what you are looking for?
http://www.modthesims.info/download.php?t=475882

I searched through MTS but for some reason this mod didn't come up! Thank you so much, looks exactly what I've been looking for...!