D-Maj    F#-Dom7    G-Maj    G#-dim     b-min / f#    F#-Dom7   G Maj    G#-dim7    D-Maj+6 / A    g#-dim7    A-Maj+4   A-Dom7   D-Maj

a second attempt, made immediately after the first attempt, to recreate the music I played while warming up (without listening back to the recording):

while warming up on June 2nd, 2015:

IMPROMPTU                     audiosatisfactory     exhibits Phases A and B activity

Both performances exhibit the ability to play a functioning cadential scheme in D Major; however, I was unable to exactly re-create the music that I had just played a minute before. The progression in the first recording first heads toward the relative minor (B minor) and then to the subdominant (G Major), whereas these actions are reversed in the second. An hour or so later, I made two attempts in front of a small audience to turn the initial warm-up fragment into a stand-alone character piece called Impromptu:

D-Maj    F#-Dom7    b-min    D-Dom7 / A    G-Maj    g#-dim7    D-Maj / A    A-Dom7    D-Maj

Just after turning on the recording device, I sat down at the piano and played these 18 seconds of music.  A basic harmonic analysis could be as follows, containing nine separate harmonies:  

This attempt, while similar, did not unfold in exactly the same way. See its respective harmonic analysis: