relay replacer

i found this old thread on the 12volt...

https://www.the12volt.com/installbay/forum_posts.asp?tid=12447&PN=0&tpn=4

on page 4, thinkster made a diagram of a "relay replacer" using transistors and resistors.  it shows exactly what i want to do...except i want a -12v output.

i have the same setup as the original poster.  i have a street glow music interface and a lot of blue and turquoise neons.   i want the neons to flash alternately but the relay is pretty loud.  i started making this "relay replacer" when i realized that the output would be +12v. 

the music interface has an on\off switch and a music/light switch.  when the switch is on "light," all the lights are on, constantly.  when switched to "music," it gives off a constant positive(+)  signal to the neons and the negative(-) signal switches on and off...on when there's a beat, and off when it's silent. 

i plan on using another switch to choose between having both the blue and turquoise neons on at the same time, or having them flash alternately.  this is why i want the -12v output.  i want to still be able to control the neons normally from the music interface.   can somebody help?

okay, to help out, this is how i originally had it set up...(the positive wire from both neons are connected to the same 12v+ source)

here is thinkster's "relay replacer"

i don't need 2 outputs any more...i'll have the blue neons set up directly to the music interface (when the MI pulses the negative signal, the blue neons should flash on).  then i'll connect the turquoise neons to the relay.  i'll hook up the turquoise neons like this...

if my logic is correct, when the blue neons flash on, the turquoise neons will turn off.  when the blue neons are off, the turquoise neons will flash on.  this way the blue neons will always be controlled by the MI.  and if i have the MI set to flash to the music, and i put a switch on the ground (pin 30) before the relay, i can add the flashing turquoise neons.

now, i still need help changing "thinkster's relay replacer."  as you can see it has two 12v+ outputs.  i think i only need one "n/o" 12v- output (if it can't be done, and there has to be two outputs, i just won't connect anything to the "n/c" output).  please help.  thanks.

I know there are doolock pulse voltage inverters, but I use them for - to + pulse, not sure if there are + to -, but they're made by Omega...

i was looking at a couple of those door lock pulse inverters, but they look just like relays...i could be wrong, but wouldn't they make a "click" just like a relay?

i was told to just change the +12v to a ground...

it doesn't look right to me, though.  i don't know about transistors, but on a relay, you need a negative and a positive for the trigger.

i want to work on this over the holidays while i have some free time.  could someone either fix this "relay replacer" for me (i need negative outputs), or just come up with a whole new diagram?  i just need something that will replace a spdt relay.   thanks.