Story/Characters: Overall the story is not bad for this period, although by even later SNES standards it's not very good (or even compared to FF4). The twist partway through comes out of nowhere but is all right, and the conclusion is acceptable. It could have used a little more dialogue and some more believable development in the "romance", but I guess this is 1992.
World: The world is mostly standard fantasy. My biggest issue is that the whole "song" theme has virtually no effect on anything. It's just a skin over a standard magic system, seemingly without even a slight attempt to introduce any music or song-based elements. The song guilds might as well be magic guilds. Perhaps I'm being overly critical because Ar Tonelico II is one of my favorite PS2 games, but they could have at least tried.
Game Flow: Most of the flow problems stem from the very slow battle system. I soon began to run from any fight that had more than 2 enemies because it just took so damn long to fight anything higher than that.
The biggest problem with progression through the game is the parts where you have to backtrack to previous towns. In the earlier parts of the game this involves walking through these long paths with random encounters every few steps. The game isn't that long but the tedious battle system and this annoying backtracking make most of the time you spend in the game wasted.
But the game is quite easy overall. The buff spells are overpowered, and the 3-note ultimate spells you get later kill almost anything in 1 or 2 hits other than bosses. The last bosses do barely any damage.
This game is very similar to Light Fantasy in that overall the game is not that bad but it's torpedoed by a horrible battle system. This game doesn't have the severe balance problems of LF, though.
System: The battle system presents an illusion of complexity because it looks like it incorporates tactical RPG elements, but it really doesn't. There are only two rows and it's just like the front and back ranks of any other game (where you place on the horizontal row makes no difference). You can attack any enemy on the board.
Everything else about the system is standard RPG. Instead of giving you a more powerful healing spell you just get the ability to use the basic healing spell at power level 2 (and then 3), but that's basically the same as having separate spells.
Side Quests/Optional Content: The instruction manual mentions jobs you can take at rumor houses in towns. There is one in the first town (retrieving a pendant from a cave and then beating a spirit that has taken over a guy in town), but that's it. I assume they intended to have more of these but ran out of development time. There are rumor houses in each town but they just give rumors, no jobs.
Interface: Overall this isn't that bad compared to other games in this period. There's a unified command button and the menus are easy to navigate. You still can't see equipment stats -- I don't understand why so many developers were so slow to add this.
Graphics/Sound: You would think given the title of the game that the music would be good, but it's just normal music. Using songs in battle (i.e. spells) doesn't change the music.
The graphics are average as well.