Prolong the sound of a word in writing

Question

How do I prolong the sound of a word in writing, while maintaining its natural sound? I want to prolong the sound of these words:

Doh
Rei
Mi
Fah
Sol

If I write Doooooh, people might read it as doooo-oh.

Answer 1

Like they do in written choral music, use hyphens between the stretched out sounds (similar to what @seagull answered) except it would not be using phonetic spellings, as in their example.

So for Do Re Mi Fa... it might be written as:

"D-o-o-o, R-e-e-e, M-I-I-I, F-a-a-a, etc.

If it was words instead of sounds, the reader probably wouldn't be confused.

Another method, again borrowed from music, is to draw a line extending out from the word to be stretched, like in this example:

Answer 2

I recall an old tactic hymn writers used to use where a dash would represent a longer vowel sound. For instance:

Do-h Re-i Mi- Fa-h So-l

etc.