This widget lets you use your computer keyboard as a piano keyboard. It gives a range of 3 octaves (1 1/2 on either side of middle C). It was originally made for singers, but should also be useful for composers, musicians, &c.
The widget adapts itself to any keyboard layout.
This is shareware with a 30-day trial period.
What's new in this version:
Version 1.5 does chord analysis.