Nathan Manufacturing

Robert Swanson founded Airchime Ltd., beginning by making custom steam whistles in his British Columbia home.

He preferred the sound of steam whistles over the single-chime horns made by Leslie and Westinghouse Air Brake Company.

In 1949, he introduced the Hexatone H5, of which some odd (88) were made according to Robert Eugene Swanson's personal manufacturing/sales records.

The H5 was only preceded by the H6, of which (4), including a cast iron H6 prototype known as the 'Iron Maiden', were only produced and never sold in any quantity to any railroad and were considered experimental.

The H-series and N-series, also rare, preceded the M-series manufactured by Nathan in the United States and Airchime Mfg.

Captain Charles Benter, who followed John Philip Sousa as Marine Corps Band conductor, played a role in developing what is called "the most melodic horn in railroading".

M5 bells tended to be varying amounts of hertz off from the diatonic keyboard, just like a chime steam whistle, so about any sound close to various chords could be heard on a healthy M5.

The second generation P-series diaphragms remained the same stainless steel, however the inlet to the power chamber was now round, due to elimination of the core in the casting pattern.

The K5H is Swanson's best yet imitation of a steam train chime whistle, heard at a distance it was described as "unresolved" and "haunting".

[6] In 1975, Deane Ellsworth, who was in charge of locomotive appliances for Amtrak, wanted to bring the superior K5 to America.

At the same time, Airchime came up with a lower-profile bracket and the new chime was called the K5LA, and it cheery chord has become very popular from the old Chessie system (first user of the K5LA) to Amtrak, Southern and many other roads The K5LA designation included a "K" for the double-diaphragm kettle drum design, an "L" because of its low-profile manifold, and an "A" for American tuning, to differentiate it from Canadian tuning.

[2] In 2005, Federal Railroad Administration regulations specified a maximum decibel level for horns, resulting in the development of the K5LLA (the extra "L" means low-pitched, with the first bell tuned to middle C) for EMD and K5HL for GE.