Alpine Aviation took over the interisland US Postal Contract from Corporate Air just about a year ago. They fly Beach 99s.
While searching the VHF airband for new frequencies that may have popped up I found a frequency that their pilots like to use to chat between aircraft.
I managed to find their "chat frequency" (Not the remote pacific air to air frequency) and have been enjoying their totally carefree conversations for a few days now.
Usually multiple aircraft of their fleet are in the air during the evening hours and I suppose the pilots themselves took the liberty of finding an "unused and unknown" area of the spectrum. These guys have great conversations to each other!
Here is one of the funniest candid transmissions yet that I've managed to archive...!

Needless to say late at night I keep them on priority frequency.
Note: These aircraft were in cruise and to my knowledge not near traffic or PHNL Bravo Airspace.
Aloha,
LorM