Speaking in ballpark figures, half of this album is Ailee being her versatile self, and the other half is Ailee moving mountains.
I usually call songs like this "diva songs", because the vocals for this need to be pushing all the way -- this isn't a song for some throwaway member of some gigantic girl group (ahem, ahem), and only a few of the better girl group singers can actually pull something like this off, "I Will Show You" is a song for one girl, one girl with a huge, show-stopping voice. And that's exactly what Ailee is. Songs like these are very particular about the voice that sings them -- smooth is okay, but they have to really be big, deep and slightly more mature voices. For example, Taeyeon and Luna have gorgeous voices and can belt notes accurately, but they're very feminine and not deep enough for songs like this. People like Hyorin or CSJH's Lina, and obviously Ailee are better suited.
That said, I personally think the song is a bit too old for Ailee. She can sing it all right, and it's obvious that the song and her really click, but she's 23, and after listening to the rest of the album, this song sounds too mature for her. Obviously we don't want her to turn into another G.NA, nor do we want her to go the cute route like IU's dark age, but the rest of the album is pretty good evidence that she can be young and keep showing off her gorgeous voice. Even the other ballads sound younger than this.
If someone else got "Evening Sky", honestly I think it wouldn't be as effective as it is with Ailee doing it. It's actually a pretty generic song on it's own, very ordinary -- what gives this that extra strong kick is the delivery, because it really turns the entire song around. Ailee not only has the emotion to make this song interesting, but the technique to accurately translate those emotions into her vocals. She's not doing any screaming or straight-out emoting during the verses, but she gives the lines all these pretty curls. By the time she does start belting, that's also when the bare melody gets a bit boring, so it gets another kick. "Evening Sky" is generic, yes, but it's also unforgiving, but if the singer knows exactly what she's doing, as Ailee does, well, you get a pretty song.
"My Love" is probably my least favorite song on the EP, but it's still pretty good, and on-par with the rest of the album. It's a song that I think I need to see performed, because right now it's subdued but the only kick it gets is courtesy of the vocals, which aren't as powerful as they are on the other songs, and it's a bit too repetitive in the wrong places. This may potentially work with a live band or some choreography though. We'll see if this ever sees the light of a performance.
This track really shows off Ailee's vocals, pulls them apart and puts them back together all in a span of three minutes. The rap part also gives the song even more oomph, as if it needed any more of it. "Shut Up" is the type of song that you can't not want to sing along too, even if majority of us can't hit the notes Ailee seems to just zoom through. This is exactly what I meant by Ailee moving mountains with an amazing song -- I'd totally give this a 5/5, maybe more.
The EP finishes off with "Heaven", Ailee's first single. I won't talk about the song itself, because I already did that earlier this year, but honestly I think it's kind of lost in relation to the rest of the album. It's a gorgeous song, yes, but the production, the style, and even the vocals, don't match the rest of the EP. Even "I Will Show You" which is also kind of not there, matches better than this.