♭  

This is the symbol I need.  U+266D is the Unicode number.  How to I replace a key on the keyboard with it?  I can't even find it if I search the Character Map for it.

An interesting question.  How did you get the "flat" character into your question?

I found it in two fonts that are installed on my Win 7 system, Arial Unicode MS and Lucinda Sans Unicode:

I was unable to find a way to map a keyboard key to a Unicode value, and this article suggests that it can't be done:  https://github.com/kiibohd/KiiConf/issues/30 (but see "Further research" below).

As a possible alternatives to using Charmap, or if you don't have either of the two fonts I mentioned, see this:  https://www.johndcook.com/blog/2008/08/17/three-ways-to-enter-unicode-characters-in-windows/

The Unicode Input utility is described here https://www.fileformat.info/tip/microsoft/enter_unicode.htm and downloaded from here (about mid-way down the page) https://www.fileformat.info/tool/unicodeinput/index.htm

This is overkill, but I guess not enough people thought that $169 was worth it:  http://www.photologic.ca/unicode_keyboard.htm

Further research:

https://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=uniipakeyboard

https://www.unicode.org/resources/keyboards.html

> How did you get the "flat" character into your question?

♭ denotes a flat key in music.

denotes a sharp key in music.

(They're the black keys on a piano.)

As I never use the ^ key I thought I might replace it with the ♭ key.  # may not be the exact symbol for sharp but its close enough for my needs. 

That was quite the comprehensive answer.  I'm sure it will take the entire weekend to get through the links!  :)  Thank you!

Used Notepad and MS Word 2003.  Held down the Alt key while pressing +266d and nothing appeared when I released the Alt key.  ??? 

I have the character saved in Notepad though.  How to replace a key on my keyboard with it?  Or set a keyboard shortcut?

You will find the symbol on this page of the complete list of UTF8 characters:

http://www.fileformat.info/info/charset/UTF-8/list.htm?start=8810

To enter it, you hold Alt, then press these keys: +266d, then release Alt.

Some applications might respond in an unexpected way to Alt d.