Notating Optional Notes

[BigKahuna13]

How do you denote "optional" notes in standard notation?

I'm transcribing a bass line where a C is sometimes played as a dotted quarter note and optionally as eighth - quarter pair. I
thought to denote it as a grace note but from looking up the definition of a grace note it needs to be a step above or below
the main note and is typically half or less the value of the main so that doesn't seem to apply.

Any help would be appreciated.

Thanks.

[Jon Simonoff]

Parenthesis around the eighth note would show that at times you play the eighth note, but not always.

[AlphaMale]

I see them as parentheses

[HaVIC5]

Parentheses usually don't mean "optional"; they are usually used to indicate ghost notes. There isn't any real common way to notate optional notes in popular music styles, since parts, especially bass parts, are often open to interpretation anyway. The way you would do it in classical nomenclature is by way of an ossia measure.

http://en.wikipedia.org/wiki/Ossia