Nero is not what determines the available write speed settings, it depends on a) the burner b) its firmware and c) the blank discs you use.
If all three components allow 1x speed you will be able to write at 1x using Nero.
Please check the details of your writer to see if this speed is generally available.
Regarding the firmware you should have a look at the website of your burner's manufacturer, they usually provide downloads of the firmware on the website - if you cannot find them you should contact them directly - different firmare versions may support different write speed settings.
As for the discs, they are usually labeled accordingly.
You could also contact the manufacturer of your burner to ask for preferred brands of blank discs.
I think that these days many blank discs really do have a minimum write speed of 4x but I am sure that, especially for professional or semi-professional audio recordings, there should be disc that will let you burn at 1x.
You can look up the write speed settings currently supported by your burner and firmware in the Nero InfoTool:http://forum.my.nero.com/index.php?showtopic=8611