In his "unauthorized autobiography" which, as you by now know, is very dear to me, Twain complains of inexperienced writers who want to be published immediately, without paying the proper dues.
Not even the most confident untrained soldier offers himself as a candidate for a brigadier-generalship, yet this is what the amateur author does. With his untrained pen he puts together his crudities and offers them to all the magazines one after the other -- that is to say, he proposes them for posts restricted to literary generals who have earned their rank and place by years and even decades of hard and honest training in the lower grades of the service.
However, I respectfully poing out that Twain's next sentence is completely wrong.
I am sure that this affront is offered to no trade but ours.
Twain gives an imaginary example of a singer with no experience, wishing to sing second tenor in a Metropolitan production of Lohengrin.
[The manager asks the singer,] "Have you ever studied music?"
"A little -- yes, by myself, at odd times, for amusement."
"You have never gone into regular and laborious training, then, for the opera, under the masters of the art?"
"No."
"Then what made you think you could do second tenor in Lohengrin?"
"I thought I could. I wanted to try. I seemed to have a voice."
"Yes, you have a voice, and with five years of diligent training under competent masters you could be successful, perhaps, but I assure you you are not ready for second tenor yet. You have a voice; you have presence; you have a noble and childlike confidence; you have a courage that is stupendous and even superhuman. These are all essentials and they are in your favor but there are other essentials in this great trade which you still lack. If you can't afford the time and labor necessary to acquire them leave opera alone and try something which does not reqauire training and experience. Go away now and try for a job in surgery."
This is where Twain was wrong. This happens every single day at the Metropolitan. Not the last paragraph -- no one at the Met, or in New York City -- has the time to give that sort of advice.