Classic Electronic Organs for sale on Ebay of interest

[beel m]

Just one tiny correction, John- the 600 had 18 general pistons. The 601 changed to 6 each pedal, swell, great, general plus the usual reversibles. Also, the pedal 32's (and I think 16's, but not positive) came from only one computer- I guess "doubling" sounded weird at such low frequencies.

This is a very early MOS. The capture action is the sequential type (only 6 generals, only one memory). Dual card readers were on all the early double-computer MOS organs. A 600 is basically two identical organs in one console, everything completely doubled. They had not refined the technology to the point of being able to have a single card reader that could switch between the two computers. Note that there are two sustain knobs, two "voicing" knobs, two Alterable Voice knobs. At least there is just one transposer knob, no doubt a huge stack of rotary switches behind that single knob!

The key contacts on each manual consisted of a double-stack of insulated leaf switches with keying totally isolated between the two computers. Any kind of accidental cross-connection between systems would create a bizarre arpeggiating or strumming of the notes as the slightly different clock frequencies interacted. There was a special remote keyer board for the pedals to be able to activate both computers from a single set of reed switches, and the stops grounded both computers through isolating diodes. I have only seen one of these in person, and it's still in use AFAIK in a nice church. Sounds great with everything doubled, even the lowest pedal stops.

[jbird604]

Thanks for that info, beel. There is one big 600 series drawknob organ that we see now and then and it must be a 601. It has six generals plus six divisionals per div. It actually has "celeste tuning" in all divisions, even in the pedals, which is rather odd IMHO.

RE: the Rodgers air sound on the 990 ... The 990 is of course very ancient Rodgers and had a rudimentary white noise generator which was enabled by the little slide switch under the keydesk. The effect was quite subtle, adding a smidgen of hiss to the audio, more or less depending on how many keys were down.

The 890 and the other large last-generation analogs have a more complex arrangement. Air sound is still injected based on the number of keys down, and that effect is adjustable by divisions. The air sound even has high, mid, and low-range components that are separately adjustable. Besides the air sound, there is "puff" which is a burst of noise keyed by each note of each unit flute or principal rank at the attack point, actually gated through by the chiff keyers.

Each of the divisional principal and flute ranks has its own adjustments for the amount of chiff and puff, so your choir flutes, for example, can have entirely an different character from your great flutes, and the swell flutes can be different from either. Sames goes for the principals. Reeds of course don't have this since it would be inappropriate.

Another subtle wind effect is the wind sag, a circuit that slightly affects the overall tuning as more and more notes are keyed simultaneously. The idea was that when you play a huge tutti chord on a pipe organ the wind pressure dips for an instant and affects the pitch. This circuit slightly pulls down the pitch of the oscillators when a large tutti chord is played in order to imitate this pipe artifact. The degree of pitch sag is adjustable, and it can be completely disabled if one doesn't like it at all.

No doubt Rodgers was feeling challenged by Allen during the 80's as Allen's digital system went through multiple generations and became more realistic. They kept refining and elaborating upon their analog system, peaking out with the 870-890-925 models with all this air sound, puff, separate unit ranks for each division, and so on.

Though I'm still a big Allen fan, I enjoy being able to tinker with these characteristics when working on a Rodgers of that era. There are some ways in which the customizing of the stops on these analogs surpasses even what one can do with a modern digital. I loved the Allen Renaissance that I used to play at another church, but the only way to significantly alter a stop on that organ -- to get a chiffier flute, for example -- was to swap out the entire set of samples for that stop using DOVE and the Matrix CD, a rather difficult and time-consuming operation. On these 1980's Rodgers organs, you can go from a completely chiff-less flute to one that barks like a xylophone with the turn of a knob.