Compose longer pieces

Hello! New subscribere here.

I was looking for some advices about composing longer pieces of music. I ask this because i noticed that since i understood the structure of shorter musical forms ( minuets, for instance), the number of bars to expose the theme , the contrasting one ecc, I never suffered creative block or something like that. But now I wanna understand how to create longer pieces. I can arrive to a maximum of 4/5 minutes, including repetitions, but then I can't go on...Maybe loosening themes?

Anothere thing i noticed while analyzing great master's compositions is in large music there is not an idea of question and answer in the melody, but a long and loose melody line...But still can't compose anything like that...have you got any advice

I'll Leave an example of what I mean.

To begin I want to ask you why you want to compose longer pieces.
In the beginning of my path to becoming a professional composer, I thought that the longer a piece is, the better it is.
This is, however, a great mistake... In the rule, longer compositions are not better than shorter pieces and vice versa.

When you want to compose longer works, you need to make sure that you do not make the music boring by endless repetitions.
Variation in the form of development is the key.
Try to develop all stated material as much as possible. 

Mahler's 5th Symphony: https://www.youtube.com/watch?v=UjmthMDpyco - An hour, pretty famous.
Weber's Symphony: https://www.youtube.com/watch?v=Xq2gwuKDPnY - 10 minutes, studied more often.

Thanks to both of you for you replies and help me reflecting about that, but I think i have a good motivation to try composing longer pieces ( which i alwas mean to be 10:00 or less). I think that taking this task i would bo forced to modulate, use accidentals and other ways to keep the music fresh and not repetitive...I've always appreciated short compositions more than long, but it would be a nice challenge to me try stretching the duration...the problem is that I have not properly clear what try to do!

I think you will want to take the time to really sit down and study some scores, as Monarcheon suggested.  Sit down with some music and a pencil and ask some concrete questions.  (If you don't want to scribble all over a good score, find a piece that is available in the public domain and can be printed off the internet for free.  You can write all over it without feeling guilty). Start by identifying the main theme.  Mark it somehow.  Mark it each time it reappears.  Look at the material that's left.  Is there a second theme?  Mark that every time it appears.  Is there a fugue?  Where is the same material repeated, but in a new key?  What is different about each time the theme is repeated?  Different instrument has the melody?  Different harmonization underneath the melody?  And then, how are the different restatements of the theme linked to each other musically?  You want to look at the large scale organization of some large works.  Don't worry about small details.  You know how to do small details already because you can write short works.  Think of it as writing an essay.  For this exercise you aren't looking at individual words or sentences.  Instead, how does each paragraph function to support the larger argument?  If you aren't confident about what to look for when studying scores, you can also read some analysis of well-known large-scale works by other people.  You can find wikipedia articles about major works that discuss their basic structure.  Read a few of those and look for patterns in the way these works are put together.  Concert programs from the local symphony, opera, etc. also often contain a page or two discussing the structure of the pieces to be performed, and how they relate to other famous works that influenced the composer.  Graduate school analyses are often published online these days and you can study them for free.  (:

Thanks @pateceramics you're answer was really helpful...and so easy than I didn't have thought about a serious analysis of form! I am already looking for some good pieces to aanlyze, both piano and small ensembles, maybe string quartet...Have you got any suggestion?
 

I'd suggest you start with pieces you already know.  If you know it, and you like it, try to figure out what the composer does that you enjoy and you can apply to your own work. If you know it, but you hate it, (had to play it for school, so you know it well, but you can't stand it), try to figure out what the composer did that you dislike so much, and you'll know what NOT to do in your own work.  There are plenty of pieces that are technically well-structured and "good" pieces, that you might not like.  Figure out why.  It can also be helpful to look at beginning work here or on youtube or sound cloud.  You'll start to see the same mistakes crop up again and again.  There is never any "wrong" answer when writing music.  People can always write whatever they want.  And yet, if you listen to enough work by beginning composers, you start to hear the same problems over and over again, and think, well if I wrote it, I would change...  It's much easier to notice these patterns in other people's work than in your own, but once you start noticing, you'll be a better critic of your own creations, and can edit them if you catch yourself falling into the more common beginner patterns.  

While I don’t compose classical type music.. I too was working at longer pieces, without endless repetitions, and mindless, variations and transposes.

I took a subscription out to Amazon Prime..  They have a very large video content..  Series that are 3 -  7 seasons long..  I’ve seen a few that are quite excellent. 
Then the analogy of long pieces of music to long video, mini-series.. etc.. hit me..  The successful 
TV series had a number of factors that made them work. 

You have a plot, an arc of the story line, which itself grows and rises over several seasons. 

Sub-plots which would get resolved in an issue, or span several episodes or even a whole season.

You primary cast of characters, which carried the plot forward

Re-occuring roles, to bring familiarity and grounding to the story line.

One off characters, good for a certain experience, and then gone..  episodes, of humor, tragedy, resolvement, suspense cliff hanging.. ominous activity that takes a time too surface. 

For instance 'The Wire', called by some as one of the greatest example to TV writing, employs quite a few powerful, obvious, and not so obvious devices.  One was Changing locations from season to season and points of view for that season.  This allowed it to go on for 5 spellbinding seasons, without endless repetition. 

The analogy for music … So another section of music could consist of your main hero’s sound,, but supporting instruments might be more varied..  More brass in one section.. 

The point of course is you want some kind of continuity and stability but don’t want to bore the listener with too much of the same.. 

My approach was to compose one or two pieces..  spread them out,  build in material between. Sometimes I had to stretch or cut times to get back to a certain style or motif.

As this slowly took shape, I began to see, where I had to have the main instrument, and motif come back in at certain points.  Other times a variation of the them, with different instruments.. 

You kind of have to step back from your first vision, (piece of music).. and see how it can grow and evolve, and ‘revisit itself also’.. 

Now sad to say, I am not familiar with classic composition, so this may seem like nonsense to some, or not ‘valid’.

But it has given me a framework..  

Also don’t be afraid to try to different pieces of music, with the proper transition between the two.  It is the brains funciion (and it does an excellent job most of the time) to take the existing data in the world, ands find ‘meaning’ in it..  

I’ve often juxtaposed two different ideas, and then marveled at how the brain, made sense of and gave meaning to it.. Sometimes 
you have to try that.. and then do some fine touching up to make the transition from one motif to another more natural sounding.. 

Of course several peoples suggestion of listening to successful long pieces is a very good first step.  

I have taken several long ‘rock pieces’  Stairway to Heaven, The Who’s Tommy’ (not so much).. Pink Floyd. and done ‘behavioral character analysis on it’..

IE.  Oboe plays a funny role early in piece,  a sadder one later.  and then a kind of ‘reflective quality at the end.  This can be likened to the ‘character development of one of the roles in long movies,   or even a human over his lifetime.. 

Reading some books on the psychology of music might not hurt either..  

I took a free course at Coursera.org. on ‘Biology as Music’..  The Human body is the greatest creation to create, listen, and enjoy  music.  In one aspect, 

@markstyles thanks a lot for the time you spent in writing you're answer. I really agree with you...I can't hope to write a long, well made, piece of music if I still have in mind a too much simple structure as, for instance, the small piano pieces, made out with just a theme, b section and theme again. I have to start thinking as an evolution in time, during the composition, where my characters grow up and I state it using all of the material I can...It is hard to think with my actual mind set...but I can remember the first struggle at my really first composing time...So it doesn't scare me that much trying a new mind set :)

@pateceramics also your suggestion is useful again! Listening to othere beginning composer can be an interesting point of view, also showing them my opinions, I surely give it a try!