[Harp-L] Blues plus

[Music Cal <macaroni9999@xxxxxxxxx>]

I have been working on blues lately (playing the chromatic). I am mostly
just keeping it simple and sticking to I-IV-V 12 bar blues. I am making
much progress yet sometimes I feel like something is lacking in certain
bars. I am hearing a vague musical expression of a fleeting feeling but
before my inner ear can recognize or be fully aware of its musical
expression the harmony transitions and the feeling, along with the vague
awareness of its musical expression, is lost. It's a vague "outside" kind
of musical sound and I seem to be tormented by this fleeting notion mostly
(but in happens elsewhere as well) on the IV chord of bar 10 of a standard
I-IV-V blues harmony. Any ideas what the musical representation of this
feeling might be (ie, some whole-tone sound, diminished sound etc)? I know
this is a vague question and this feeling may not be universal but maybe
others have had a similar struggle and could shed some light.