electromyogram vs myogram

electromyogram and myogram both are nouns.

Word	Noun	Adjective	Verb	Adverb
electromyogram	Yes	No	No	No
myogram	Yes	No	No	No

As nouns, myogram is a hypernym of electromyogram; that is, myogram is a word with a broader meaning than electromyogram:

electromyogram: a graphical record of electric currents associated with muscle contractions
myogram: a graphical recording of muscle activity

electromyogram (noun)	myogram (noun)
a graphical record of electric currents associated with muscle contractions	a graphical recording of muscle activity