1)   Click MusicalKEYS 3
Click MusicalKEYS is a free onscreen MIDI musical keyboard. With 127 different instruments, you can play the best music of your choice. Click MusicalKEYS can record your favorite tunes so that you can replay them later.

 2)   mTrax 2.8.5.1
Slow Down Your MP3s, Learn Solos Fast! Control Tempo, Pitch, Loops and More! mTrax will help you become a better musician by making it easy for you to learn all your favorite songs, solos and riffs; any song, any instrument!

 3)   ARPTON Synthesizer-Arpeggiator-Player 1.1a
All-in-one MIDI musical instrument with Arpeggiator and MIDI / MIDI Karaoke Player. Works with any hardware or software synthesizer installed in your computer. Allows to play piano on PC keyboard with any MIDI file and sing at the same time.

 4)   ARPTON Lite - Synthesizer-Arpeggiator 1.2h
All-in-one MIDI musical instrument with Arpeggiator and MIDI / MIDI Karaoke Player (Lite version). Works with any synthesizer installed in your computer. Allows to play piano on PC keyboard with any MIDI file and sing at the same time.