Notating octaves?

Originally Posted by Justin Tokke

No one has yet considered electronic instruments where the 15mb would certainly come into use. Extreme lowness!

Actually, a piano already comes very close to the lowest possible tone a human can hear. An A0, as the lowest piano tone, has a frequency of about 28 Hz, and humans can hear from about 20 Hz, which would be a D#0, so only a tritone below the lowest piano key. Sounds unbelievable but it's true! (And even if you say you can hear to 18 Hz or so, that only makes it about a half tone lower). (In the upper register however, we can hear up to slightly more than two octaves above the highest piano tone. As a random additional note, this of course also means that in the highest register of the piano we can only hear the overtones up to about the fourth partial, which explains why this register always sounds a bit duller than a bit lower tones.)

But to get back on topic: While writing a D#0 with a mere 8vb would still require quite a few ledger lines, it would still be quite readable. (Of course, using an 15ma bassa would work very fine too in such a case, I'm just saying it wouldn't be -necessary-).

Flint is 110% right on here.

Before trying a less-than-standard notation device, you should try to use the most standard notational device possible to get the correct effect.

If we are refering specifically to the example posted above, I think that there are three perfectly standard means of approaching the notation would:
1. tiny clefs, one treble one bass, right above one another, just before the intended notes;
2. the addition of a third staff for the single bass note;
3. or placing material of BOTH treble staves into a single staff, and making the second staff a bass clef staff.

I prefer the 3rd choice.