Hello,

In the section "Practical Work with Color and Sound" of the "Principles of Color and Sound" chapter in the CGD book, it specifies "you will need a musical instrument that does not require the use of your mouth". I'm wondering if this is because that's easier for untrained singers to match, or if there is some occult significance precluding the use of e.g. a pitch pipe for this purpose.

Thanks,
Heather