Improvisation at the Piano

1) do repeated notes (repeat notes of the melody, or repeat notes to emphasize your rhythm, or both)
2) trills - do a trill on an important note in the melody
3) upper neighbor - use a note a m2nd or M2nd higher as decoration for your melody - and so on with all these suggestions below..
4) lower neigbor
5) grace notes
6) scale (decide what scale you are going to use, at any point in the song, to fill or embellish the melody)
7) change harmony (chords) on the same melody note
8) skipped notes (example: interval of a third)
9) create a line (musical pattern) using inversions of the chord, ending on a melody note
10) When improvising ("on the fly") when in doubt where to land, come back to the root of the chord. 
11) Create a rhythmic pattern with the chords underpinning the melody 
12) invert the melody (turn it upside down) while maintaining the same rhythm 
13) Choose a major scale, blues scale, minor scale, diminished scale to fill spaces
14) Use a tritone for effect
15) Use different harmonies for the same melody
16) Use chromatic passing tones while filling those "spaces"
How man other ideas can you think of to improvise on a melody line?

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