Avid's Sibelius software is a long-established tool used by composers and musicians of all levels to create professional musical scores on their computers. Going beyond what most DAWs can do in the field of scoring, it's a serious package. But it also costs money - so now the company has released an introductory version. Called Sibelius First, it's completely free.
As you might have guessed, its feature set is more limited than its other family members but it's still a great way to get started. It supports up to 4 instrument parts, transcription, editing, and cloud sync among some other functions. Up to 10 scores can be stored and shared in the cloud.
You'll need to create a free account to download the software, and if you find you need more functionality in future you can upgrade to Sibelius or Sibelius Ultimate to unlock tons more tools.
Learn more about Sibelius and scoring in the Ask.Audio Academy: https://ask.audio/academy?nleloc=category/audio/application/sibelius