how do you become a classical music composer? also how do you learn about it?

There’s no step-by-step process. It’s really a live-and-learn type thing. Each composers’ story is different, but here’s mine, which will give you some idea on how I started composing. I started taking piano lessons when I was 8 and became pretty accomplished by high school, getting hired out by theater companies to direct orchestras and accompany. I started keeping a record of the pieces I liked and why I liked them, taking snippets of the sheet music I liked and filing them. I wanted to know why they made me tick. I started just messing around the piano, finding something I liked, then gradually forming it into a piece. I started to orchestrate piano pieces for fun, which enabled me to discover the potentials for each instrument and what was possible with instrumentation. In addition to all this, I learned music theory which provided a basis for analyzing music on its most fundamental level. Throughout high school, I mostly fooled around, and began experimenting with classical forms like sonatas, symphonies, etc., training myself to make the music fit the form. It’s a good excercise to do, forcing you to be simultaneously discriminate and creative. Then, I got accepted to conservatory and underwent many compositional excercises, writing, rewriting, writing, rewriting. These took the form of preludes, concertos, etudes, and both small and large orchestral pieces. The aim of these excercises was to utilizes the resources of melodic line, harmony, dynamics, rhythm, musical form, and instrumentation to their utmost potentials to match whatever goal I had for the piece. Music composition differs from any other art form in that it is the most abstract, so having this “goal” is usually not directly perceived in the music. But all these factors should be working toward whatever you’re trying to get across (likewise, not using these factors to their utmost potential is a goal in itself). Composing a pretty melodic line with interesting harmonies is only the first step: you need to then examine the relationship between the notes, between rhythm and the notes, etc. so you can have some sense of development–or lack thereof if that’s your goal. Make everything, absolutely everything count. You can’t exhaust the ways of making everything in the piece worthwhile. I suggest listening to your favorite pieces to figure out why they “get” to you, then, utilizing the tools of music theory, examine them on their most fundamental levels. Then, start composing pieces, perhaps a small prelude on your instrument (if you play an instrument, that is…not all composers have one). Then, work up to small chamber settings, then orchestral. I suggest writing in classical forms to really work you. Write and rewrite should be common words in your category. And don’t forget to investigate orchestration. Rimsky-Korsakov’s famed work on that subject, I know, for a fact is available in the public domain, perhaps online.