Other chords that you will occasionally see in sheet music involve a slight alteration to one of the given formulas. The alteration is usually indicated in the name given to the chord. Consider the following examples:
The C7b5 chord is just as the name implies; a C7 chord with the fifth note flattened.
The G7#9 chord involves sharpening the 9th note of the G9 chord. Another type of alteration occurs when chord symbols are written thus:
Example 1: G/F# bass. This indicates that a G chord is played, but using as F# note in the bass.
Example 2: C/G bass. This indicates a C chord with a G bass note. Sometimes the word "bass" will not be written (i.e., the symbol will be just G/F#), but the same meaning is implied.