Anvil Studio is a free music application for Windows which was designed for people who want to: record music with MIDI and Audio equipment, compose music for MIDI and Audio equipment, sequence music with MIDI equipment or play with music using a computer. It is a freeware music recording application that's light on system resources, straightforward and well-designed.
Here are some screenshots to illustrate the features and user interface of this application:
Synthesia
MuseScore
Virtual MIDI Piano Keyboard
Everyone Piano
Hydrogen