Online Bass Instruction with Rusty Springfield
Chord Symbols

Some chords have several symbols. We'll use the key of "C" for our examples.
CMaj7, Cma7, or CM7

This chord is sometimes also notated with a triangle between the "C" and "7". This can create some confusion, especially when the copyist writes quickly and the triangle resembles a circle, indicating a diminished chord! A single "M" after the "C" can also be confused with a small "m", which denotes a minor chord. Needless to say, if you are playing along in the chart and mistakenly choose the wrong chord, the rest of the band will sure look at you funny. For this reason, I recommend using the very obvious "CMaj7" symbol. No confusion there.
C-7, Cm7, or Cmin7

The "C-7" symbol is my personal choice, and is commonly used in professional circles, especially jazz.
Cdim7 or Cº7

This chord is sometimes notated with a small upper circle between the "C" and "7." If you choose to use this method, be sure to make the "o" very round, so as not to be mistaken for a triangle, which is shorthand for a major chord!
C-7(b5)

This chord is also sometimes called a "half diminished," and notated with a small slashed circle between the "C" and the "7." At Berklee, my alma mater, this practice was frowned upon, in favor of calling the chord exactly what it is. A "C minor 7 flat 5." Again, this eliminates any question of the exact nature of the chord.
C7(#5)

This chord is also called a "C7+5" or a "C augmented 7." In the interest of continuity, "C7(#5)" is the most specific choice.
C7sus4 or C7sus

Same chord, in shorthand.
C5

This is the symbol for the beloved "power chord." which consists of a root, it's fifth, and usually the octave of the root on top. It is technically neither major nor minor, since it does not contain a third. It's major or minor sound is implied by the melody it accompanies.
C(9) or Cadd9

This triad with the ninth on top can be written either way. Some prefer the second, more obvious, method. I've also seen this chord referred to as a "C2" chord, although this is not standard notation. (Remember that the ninth is the same note as the second, but played an octave higher.)
Altered Chords

"C7 alt." is a symbol that can lead to many interpretations. It denotes that a chord tone (a 5,9,11,13) has been changed to create a more complex color. "Which one?" you ask. Good question. I wouldn't know either. A much better method is to spell out the exact chord. eg: C7(b5#9) This takes a little longer to write, but it alleviates the guesswork.
Go to the next lesson: Chords Built On Scale Intervals