Avid Sibelius is described as 'Sibelius is a scorewriter program, created by Sibelius Software (now part of Avid Technology) for Microsoft Windows, OS X, and historically RISC OS' and is an app in the Audio & Music category. There are more than 50 alternatives to Avid Sibelius for a variety of platforms, including Windows, Mac, Linux, iPad and iPhone. The best alternative is MuseScore, which is both free and Open Source. Other great apps like Avid Sibelius are Guitar Pro (Paid), Rosegarden (Free, Open Source), Dorico (Freemium) and LilyPond (Free, Open Source).
NoteWorthy Composer is a graphical score editor intended for the creation of sheet music, but it can also import and export MIDI and Karaoke files and can export graphical WMFs. The user interface works either from the keyboard or the mouse.
Chordsheet Maker is the quickest and most efficient way to create a chord sheet or lead sheet directly on your iPad. Skip the paper and share it in PDF as soon as it’s done. No complex menus or navigation. All the necessary, in an ergonomic way.
EasyABC allows you to edit and play abc files. It supports conversion from MusicXML and MIDI to ABC. The latter uses a custom implementation (midi2abc is not used) in order to produce very readable ABC output. Direct midi input is supported for people with a midi keyboard.
Noteflight is an amazing online notation editor. On the free version you get 10+ instruments to choose from, lots of musical symbols and more. On the payed version (Cresendo) you get lots more instruments, guitar tab and sharing options. Best way to wite music on the web.
Canorus is a free cross-platform music score editor. It supports an unlimited number and length of staffs, polyphony, a MIDI playback of notes, chord markings, lyrics, import/export filters to formats like MIDI, MusicXML, ABC Music, MusiXTeX and LilyPond.
Melody Assistant is dedicated to music writing, printing and rendering. Easy to use, Melody Assistant offers a user-friendly interface and powerful capabilities. Now used by a very active community of thousands of people, it has become a favored tool for creating music.