29.8Build harmony from melody + bass

Suppose:

RH melody = G

LH bass = C

Likely harmony could be C.

Add E.

Now:

C-E-G.

Next:

RH melody F

LH bass B.

Possible harmony:

G7/B

Add D or G.

Now:

B-D-F-G.

Next:

RH melody E

LH bass A.

Possible harmony:

Am.

Add C.

You have:

C → G7/B → Am

created from two moving lines.