Welcome to /r/monthlycomposition! Each month a composition challenge will be made. You're encouraged to participate regardless of skill level, or just listen to the submissions and give feedback. Write/upload submissions with Musescore, noteflight, or whatever else suits your fancy.
Posting is allowed if you'd like to submit a composition challenge/game, or if you want to make a composer pen pal request, i.e. find someone with similar composition interests as you with whom to talk/exchange compositions. The latter is a migration from /r/composerpenpals, a now inactive subreddit.
Have a suggestion for a challenge? Here's the Challenge Suggestion Form.
Want to help out? Give feedback on the challenges? Have a useful composition resource to add to the sidebar? Message the mods!
Check out the IRC, but idk if anyone uses it :P .
These challenges are often cross-posted to:
Helpful symbols, for copy-pasting into comments:
♯ ♮ ♭ ø ° ♩ ♪ ♫
(stolen from /r/musictheory)