Ah, so a voltage divider. Got it. If so:

Schematic 9v supply only
+14 +9
Ground +4.5
-14 0

Next. Your incoming signal arrives already referenced to ground, and you need to send the outgoing signal on its way reference to ground, so you need to change the reference. You need to capacitively couple the output, and then put a resistor to 0V.
The same applies to the input, but you first need a resistor to real ground (put it between the jack and C1), then a capacitor (C1), then a resistor to your new artificial ground (R2).
I think 10M is a bit large for R2 - 1M would be plenty.

 

OK. I am beginning to understand. Probably easiest to just use the circuit as it's designed at +/14v. But it's good for me to understand the difference. Thanks.

 

So if I do use the Max1044, it creates taps of +16.2, -8.6 and +4.5. So I think the +4.5 would be a virtual ground with the rails at +16.2 and -8.6. +4.5 is close to the middle of the rails, but not exactly. +3.8 would be exactly in the middle. Right?

 

Another option, I recently built a pedal that used the Traco TEC 3-0923. It accepts 4.5-13.2v and outputs +/- 15v with 100 mA output.

 

Another option, I recently built a pedal that used the Traco TEC 3-0923. It accepts 4.5-13.2v and outputs +/- 15v with 100 mA output.

That is exactly what I would do.
However, 3 watts is much more than what you require. In order to maximize battery life, I would go for the 2 watt version, TEC 2-0923.
The reason being that these devices are more efficient at close to their maximum load.

 

Here is the circuit for that TEC. Good point about the 2W version.
As for batteries, very few musicians use them and opt for 9-18v isolated power supplies. I use a Cioks.

 

The crème de la crème of acoustic guitar preamps is by a company called Grace Designs. Of their 3 instrument preamps, Felix, Alix, Bix, the bigger two run on AC with rails at +/-18. While the smaller Bix runs on 9vdc and has +/-15v rails. They probably used something very similar to the TEC in the BIX. These 3 have different levels of EQ, but the preamp is dead quiet with a lot of gain.