Jazz++ is described as 'MIDI sequencer/composer. Create your own music' and is an app in the Audio & Music category. There are more than 25 alternatives to Jazz++ for a variety of platforms, including Windows, Mac, Linux, Android and iPhone. The best alternative is MuseScore, which is both free and Open Source. Other great apps like Jazz++ are TuxGuitar (Free, Open Source), Guitar Pro (Paid), Rosegarden (Free, Open Source) and LilyPond (Free, Open Source).
Band-in-a-Box is an intelligent automatic accompaniment program. You can hear and play along to many song ideas and go from "nothing" to "something" in a very short period of time with Band-in-a-Box as your "on demand" backup band.
alphaTab is a cross platform music notation and guitar tablature rendering library. You can use alphaTab within your own website or application to load music sheets from files like Guitar Pro or use the built in markup named alphaTex.
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.
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.
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.