Structure:
I want to accept as true everything about you was sincere. Everything that rolled off your tongue was silky-smooth. You made me feel anything was possible. I  was lost in your beautiful deceit. You had a way about you that made even the Gods heave a sigh. The things we would  could do. The mountains we could climb.

I  want to accept as true everything about you was sincere. Everything that rolled off your tongue was silky-smooth. You made me feel anything was possible. I  was lost in your beautiful deceit. You had a way about you that made even the Gods heave a sigh. The things we would  could do. The mountains we could climb.

His secret is that for some mysterious reason he cannot die. He has been alive since 1901, when he was about 20 years old something happened to him that froze his physical appearance and subsequently he has not aged nor, apparently, can he be killed. His body just heals itself.
He learned the piano playing in speakeasies in Chicago during the prohibition, some time after the mystery event that caused his affliction. If he stays in one place too long people start to notice that he doesn't get any older or can't be fatally injured. Now government scientists are after him to use him as a guinea pig in an attempt to create an infallible super-race and he is forced to run for cover, adopting a new identity, each time they catch up with him.
But something more deadly than the scientists is also on his trail, something connected to the mystery event that left him practically immortal. Something that wants to take back his gift/curse.
He wants rid of it more than anything but he knows when that happens he will die.

Plot:
 As a child, he was raised on classical music and loaded promises. His father was a workaholic; he showed no interest in the family, but supported it, begrudgingly. The mother was a zealous perfectionist. The son showed a lot of aptitude in piano early on. His sister was slightly autistic....and very sickly. She was constantly in and out of the hospital.

The boy loved her with all his heart. He practiced in front of her often, with an instructor. The instructor was from Argentina, and was most apt playing jazz . And for some reason, the sister took to this brand of music the most.

They grow, the family wasn't doing well financially, and the daughter's ailing condition made things even more difficult. Soon,  the father grew to abuse not just the daughter but also the boy.  One day, she died of unknown causes. The boy  was devastated, and suspicious. He accused his father, and killed him in a fit of rage. He moved south, with nothing but a backpack and a stack of blank music sheets. He found his old instructor after some time, lived with him. One day, he met a beautiful girl. He had a strange name, but she felt there was something familiar about him, and about his music..

Structure:
I'd say make use of flashbacks, maybe to elaborate more on what happens to the sister. Leave alot to be gathered in the end, like whether or not his murder was justified? That will sculpt the climax. Maybe he's managed to phase out some memories completely, which could add more depth. The mother might have done it.

Tone/Voice:
Like ctrdragon, I was shooting for more of a Heart of Darkness feel.

Plot:
I just read Elmore Leonard and Stephen King's books about writing and they both said they never consider a plot line.

Plot:
His secret past :  Adventurer,  people hired him when they wanted to find something, or explore something they've found, Holy Grail, Pyramids, other known objects and places.

Why He Plays the Piano: His old Partner and Lover used to love Jazz, that's how they met, she died during their his last journey.  This is one reason he keeps it a secret, that and a few other reasons.

Future: Unfortunately being the best at your craft means that no matter how hard you try to escape it, they always try to pull you back in.  After all the why would he be in Buenos Ares if he wasn't already looking for "insert artifact here" anyways

Plot:
I know how cliche this will sound, but the guy doesn't seem to really have anything interesting about him other than his secret past.

Have someone from his past come into his quiet life, or have his girlfriend be a reporter or something and find out about his dark secret and maybe publish it.

If your story is crime or action, he could have been in a mafia and be in the witness protection program or just go into hiding without the government and the mob boss finds him.

If you want the book to end angsty then have his girlfriend either leave him or die at the end.

If you want fantasy he could be a faery prince that ran away from his kingdom or perhaps a demon escaped from Hell. He even could be a fallen angel and have heaven be more sinister than what the general perception is. Like maybe they are actually planning to destroy the human population.

Character Development:
In the beginning he should look boring and uninteresting. But as the story progresses the outlook of him will increase and the reader's will begin to see his 'value'.

But this all depends on what audience you are reaching for. If it's the 'normal' crowd, then they might get to bored in the beginning, but if it's for people with a higher intelligence or simply more time on their hands, they might enjoy a more complicated story line.

Tone/Voice:
A detached sort of feel. Like Heart of Darkness, you know whats going on, but it feels more like your in a dream then actually witnessing it.

I think that everything should be from a different persons perspective than the main guy's. Use what his girlfriend sees and notices to create the story. Or from many different people around him and not just one person but not giving him a chance to have a say anything in the story.

Are writers restricted to submitting only one plot line?

Plot:
Your guy is a gaurdian angel on earth who gets jobs to protect important people from time to time, this he swore was going to be his last job. This job was to protect a female army vet, and on a fateful day he is pulled to come protect her while she's out with her best friend, a psychic. He stops the car from hitting her and senses that whilw in his angelic form is noticed by the friend and leaves, who he falls in love with. He is now torn between falling in love with this girl, or keeping her friend alive.

the jazz pianist is originally from san fransico. in his past he was a member of a corporate espionage group. he uncovered a secret formuls that a major water-bottling company was planning to use in their product to americans. he then stole it and fled the country changing his identity. now he knows THEY are hunting him down...he learned to play the piano which has a hidden compartment in it with the disk!!

When I'm stuck, I try to really know my characters and then I start asking "What if..."    Okay - what if he committed some kind of crime in his past,  What if he belonged to the Mob in the past and he has bad folks looking for him,  what if he was married in the past (either he ran out on his wife or maybe his wife died and she was the love of his life).   Hope that helps a little.

Plot:
The secret past you mentioned can come back around his girlfriend. Since you mention that she doesn't know about the past, it can be something he is trying to hide from her. Since I don't know what that past actually is, I can't really give you a specific answer, but an idea would be maybe he gets arrested for something he was running away from. Or the authorities are after him and he makes a run for it.

Plot:
Buenos Aires. Secret past. Obscure pianist. Idea--his grandfather was an SS officer in Nazi Germany. Jewish Defense League is searching for the grandfather. The grandfather--Hans--was coerced into joining the SS.  During the war, Hans secretly saved many Jews from the ovens, and was successful in not being caught by other Nazis.  However, there is no paper trail to prove Hans actually helped Jews. Hans is labeled a war criminal. It is up to Hans' grandson to prove that his grandfather really was NOT a war criminal, but instead a saviour to many Jews. How will he prove his grandfather's innocence?

it might sound really strange, but why don't you just try asking? i mean you can't really ask, but sometimes when I'm stuck i think very hard on my character until i understand their story. it's really hard for me to just make up a plot and stick a character in it. every character has their own individual story, just like every person. i hope it helps!

General:
A man sold his soul to the devil to play a grand piano.

Plot:
While residing in the urban jungle that is Buenos Aeries, your character is conflicted by past decisions and recent hauntings that is threatening his current relationship, not to mention his life. When a mysterious man in black introduces himself at the local lounge he plays, the musician realizes that his time is cut short. The moment has come to pay the demon what he had promised years ago.

Character Development:
The Jazz artist in the past may have suffered from a long-term addiction like alcohol. Relate to how performing is almost familiar to him as being once under the influence; playing piano keeps his form of deviant addiction alive; his songs are mournful, yet beautiful. The significant other could be tender yet tenacious. Some thing has entered into their lives that is now threatening them, and out of a glimpse of hope and desperation, they seek the power to fight it back, and find a new meaning to their relationship that they had never thought could exist.

Structure:
Write flashbacks of his past to particular moments you want to come alive.

Tone/Voice:
First person.

General:
Use subtext.   Outside the relationship, explore the struggle of the jazz artist to improvise.  Let the reader begin to see the connection between improvisation and how we must all improvise in life when it comes to meaningful relationships.



Plot:
Dovetail the relationship story with another crisis. Could be the difficulty of making it as a jazz artist today. Or, if he's successful, maybe it's a crisis regarding his playing ability (the note he can't reach) or the composition that won't crystallize.


Character Development:
Conflicts and how your character responds to them will develop character. I can imagine him as selfish at first, as an artist must be to his/her art, and this impacts his relationship with others.

Structure:
Tell parallel stories about great jazz artists and their relationships with women. 

Tone/Voice:
 I'd try first person on this one.

Plot:
Well, what if his girlfriend finds out that he is hiding something from her? And his girlfriend invades his private journal and finds out his deepest most darkest secret, and threatens to tell everyone his secret unless he tells her about his secret pass.