Ah, Memories... I built a number of simpler devices in the '70s for the Livonia Mich. Jaycees haunted house. I used 8 track players and rewired the track change contacts (which trip by a metal foil strip on the tape) to a SPDT relay so the relay latched through the NO contacts when the foil passed. The NC contact was wired to the tape player power lead. The room operator had a normally closed pushbutton in series with the relay coil which would drop the relay out and start the player.

Eight track carts are all loops, so we opened them up and snipped out most of the tape to get a short play time. We had a 12 volt buss running through the entire Haunted House and when you powered up the buss at the beginning of the shift, all the 8 tracks would come on screaming until the cartridges cycled through.

Sorry about the parts list, folks, and then I swapped K1 & K2 in my comment to correct it.
Let's try this again:

K1 12vac relay 850-0546, can be 886-2277;
K1 24vac relay can be 850-0374 (*) or 850-0511 (*);
K2 12vdc relay should be 886-2545;
SCR 2N5062G, can be 2N5064G (200v), 568-0640.

* 850-0374 and 850-0511 require octal socket, 850-2090.

I'm giving alternates for both AC relays because stock is low for all but the 850-0511.

Sorry about the parts list, folks. This might get hard to read if line breaks are not preserved, but here goes:

K1 12vdc relay should be 886-2545;
K2 12vac relay 850-0546, can be 886-2277;
K2 24vac relay can be 850-0374 (*) or 850-0511 (*);
SCR 2N5062G, can be 2N5064G (200v), 568-0640.

* 850-0374 and 850-0511 require octal socket, 850-2090.

I'm giving alternates for both AC relays because stock is low for all but the 850-0511.

Part 866-2554 relay, 12vdc does not exist in Allieds database. Same for 866-2020. SCR-5680639 is not in stock at all in Allied's catalog. And, Relay K1 - comes up as a 4-pole DT relay. Can be used, I guess. Since Allied is sponsering this, does anyone bother to check the parts lists for these project to see if they are correct and if the parts are in stock?