Music Theory / Piano Question

[Don Claybrook]

This may qualify as a dumb question, but here goes anyway...


In all of the books and web pages I’ve seen, the key of C is used as an example. This is understandable; no sharps, no flats, easy. Any diatonic chord I play will consist of white keys. My question is about keys other than C.

For example, in the key of B-flat, the B and the E are flatted, so that the scale is:
Bb-C-D-Eb-F-G-A.

If a “II” chord is called for, should I play C-Eb-G, staying in the Bb scale?
Or should I play C-E-G, e.g., the major triad built on the first degree of the C scale?

If a song is in the key of B, the scale looks like this:
B-C#-D#-E-F#-G#-A#
If I see notation calling for a D chord to be played, should I:
-play D#-F#-A# (in keeping with the B-major scale), or,
-play D-F#-A (the major triad on the first degree of the D-major scale)?

I guess I’m wondering if chord notations are absolute, or if they’re seen within the context of a given key (or is it a trick question…does one see this both ways depending on the type of notation)?

Bonus question: does anyone know of a website that shows lots of triads and 7ths in all the keys, as opposed to just in the key of C?

Thanks very much.