Pet Sounds was released in May, 1966, so it has to predate that.
It is my understanding that Brian recorded his dogs barking, and then overdubbed them onto an existing recording of a passing train. The train recording could have come from a sound effects album or a production sound effects library, so there is no telling how old the train recording is. However, the fact that it is hi-fi would suggest that it must be from the 1950s or later.
Here it is. The train arrives at around the 2:16 mark.
Note that particularly good transcription of liner notes in the associated YouTube video. To quote here (in case anyone has trouble accessing the video later):
“Scene One: No. 58, the Owl from Oakland is captured at Edison, a few miles east of Bakersfield on the mountain district of the San Joaquin Division. Rolling at a good 70 MPH across the flatlands before assaulting the “Loop”, three EMD (Electro-Motive Division of General Motors) F-7 units geared for passenger service startle the world at 4:50 A.M.”
(Incidentally, Scene Two features this same train closer to Tehachapi (amusingly referred to as “Tehachappi” in the liner notes) along with a military train…)
Interestingly enough, it might be technically possible to actually answer this.
One of the comments to the ‘video’ mentioned that train orders for at least one of the specific trains involved a special note to ‘whistle freely’ as a recording outfit was going to be present. They even mentioned the name of the engineer who had told them the detail (I believe this was from the Coast Lark with the 3 E units).
Should be possible to track down the date(s) involved from surviving copies of train orders, and perhaps compare this with individual lead units assigned, and thence to photographs of locomotives in this service at corresponding time. Meanwhile … wouldn’t the rear helpers going up Tehachapi be a dedicated set for a few days or weeks, or be ‘recognizable’ from photos as the interestingly-mismatched set?
Vince, give Mike his marching orders and turn him loose… [:D]