Allen Mos-1 question

[telecoustic83]

Hi folks,

The church I play for has finally upgraded its organ from an old analog conn to an Allen mos1 (283c I believe). Digital organs to me are a bit new (technology wise) being I've been used to either pipe or analog electronic. I've noticed a few quirks about the organ and I thought I'd check up and see if they were normal of these early digital machines or if I should attempt to fix it or have someone address the issues. Tremulants: if I draw a registration on the swell with tremolo and couple it to the great it comes out un-tremmed when played on the great manual. Perfectly normal when played on the swell manual though. Couplers: when I couple the swell to great and also use the great to pedal coupler, it also plays the swell on the pedal. Sharp tuning effect on great: the Allen rep told us when we previewed the organ that this effect was to give a detuned effect between great and swell when coupled together which should add to the realism of the pipe like sound. However I only really notice it when I play left hand on the swell and right on the great (both manuals coupled together of course). Both hands on the great and it's back to the perfectly in tune sound. Overall I'm very pleased with the instrument and being as old of an instrument as it is has a fantastic sound but I was curious if this was typical of the early digital technology or if there is an issue that needs corrected. Thanks ahead of time for the help and I look forward to chatting with everyone about this.

Dave

[Admin]

Hi folks,

Tremulants: if I draw a registration on the swell with tremolo and couple it to the great it comes out un-tremmed when played on the great manual. Perfectly normal when played on the swell manual though. Couplers: when I couple the swell to great and also use the great to pedal coupler, it also plays the swell on the pedal. Sharp tuning effect on great: the Allen rep told us when we previewed the organ that this effect was to give a detuned effect between great and swell when coupled together which should add to the realism of the pipe like sound. However I only really notice it when I play left hand on the swell and right on the great (both manuals coupled together of course). Both hands on the great and it's back to the perfectly in tune sound. Overall I'm very pleased with the instrument and being as old of an instrument as it is has a fantastic sound but I was curious if this was typical of the early digital technology or if there is an issue that needs corrected. Thanks ahead of time for the help and I look forward to chatting with everyone about this.

Dave

These behaviors are normal for a MOS-1. Coupling is synthetic in that the notes from the coupled manual are actually duplicated by the channel/computer being coupled to. This means they take on the characteristics of the target division - trem, tuning, etc. In addition because the coupled stops from the swell are actually regenerated for the great, they will couple down to the pedal with the great.

[beel m]

Right! And the reason for that (I sold MOS-1's) is that if it were a "natural" (normal) coupler, it would eat up polyphony. If you played 5 notes on the Great with SW-Gt coupler on, it would use 10 of the 12 available notes. If you have both SW-PED and GT-PED on, which are normal couplers, each pedal note played would take 3 notes. You can see how it's necessary to be frugal with polyphony!
There's a way to have "natural" SW-GT coupling, which our resident Allen techs can tell you how to do if you're qualified. I added a "natural" SW-GT coupler to our S301, but as stated above, when using it I have to watch how many notes I play!
R, Bill Miller

These behaviors are normal for a MOS-1. Coupling is synthetic in that the notes from the coupled manual are actually duplicated by the channel/computer being coupled to. This means they take on the characteristics of the target division - trem, tuning, etc. In addition because the coupled stops from the swell are actually regenerated for the great, they will couple down to the pedal with the great.

[telecoustic83]

I had a hunch that was what was going on, but I just wasn't quite sure. Thanks so much for the help, it's very much appreciated!

Dave

[jbird604]

Echoing all that's been said above. As to the "detuning" effect and its usefulness -- on several occasions I have modifed a MOS1 organ so that you can have BOTH synthetic and natural coupling from swell to great, simultaneously with the "sharp tuning" function. This requires adding some diodes and jumpers so that this dual coupling takes place automatically with the Sharp Tuning tab. In other words, you modify the Sharp Tuning tab's function so that it makes three things happen at once: synthetic sw-to-gt, natural sw-to-gt, and great sharp tuning.

When you activate this tab, what happens is that any stops you have drawn on the swell are coupled TWICE to the great. Once (synthetically) so that they take on the sharp tuning of the great, and secondly (naturally) so that they retain the regular tuning of the swell. What you will hear is a pretty good celeste. And any stop or combination of stops that you draw on the swell will play on the great as a celeste. This is in fact the way Allen implements "celeste effect" on certain models that didn't have doubling on the choir manual. The only flaw to the sound is that the normal and sharp pitches come out the same speaker, which is not as pretty an effect as when they come from separate computers and therefore separate amps and speakers, as in the larger doubled organs.

Two major drawbacks when using this effect. (1) as state above, each note you depress takes two of the available 12 keyers, so you can never play more than 6 notes at a time with this effect engaged. If you are playing a pedal note as well, you musn't play more than 5 on the manual. This might be somewhat limiting, but you can manage this limitation if you pay attention.

(2) Obviously, both your keyboards are now tied up just playing what is in effect one registration. So you can't, for example, play your celeste as an accompaniment to a solo stop on the other manual, since the two manuals can no longer be registered separately. Of course, you CAN reverse that idea and play a solo on the great celeste while accompanying on the un-celesting swell, but that sort of defeats the purpose of the celeste.

This is an easy mod if you have the MOS manual and can see which pins on which plugs have to be jumpered to the tab to make this happen. A diode must be included on each jumper to prevent interactions among the boards involved. I think somewhere on the forum you might find my description of how it's done, if you want to try it.

But the MOS1 system does still sound nice without any modification. Another poster recently mentioned having bought the Harrison Labs Traveling Wave Generator and DSP for his MOS1 organ, and finding that it made a great improvement in the sound. I personally haven't tried it, but I suspect it might be a nice upgrade, if it makes the sound seem less sterile and pitch-locked.

[telecoustic83]

Bill and John,

Thanks for the insight on modifying the organ to have a Celeste effect. The polyphony problem of course concerns me as I normally don't play too heavily on the notes, but sometimes I do have the tendency to get carried away. I've got a bit much on my plate at the moment to endure a potential project, but in the future I may explore modifying the organ to see how it works out. My home organ being an old 650 I've always enjoyed the chorus effect and I've often said to myself that I'd love to have that on the Allen at church which would be the cherry on the cake for its sound. I've seen those Harrison labs modules that you mentioned John and I've often thought about putting those on the organ, but having never heard them I'm a bit reluctant to spend $300+ of my own money to modify the organ ( and hope the church would offer to reimburse me for improving the sound of the organ, which it alone was like pulling teeth to get the church to buy. Thanks again for all the insight on these digital organs, I greatly appreciate it!

[Admin]

Regarding the Harrison products, the TWG is a phaser, aka chorus generator, and the Ambience DSP is a reverb unit. There are more cost effective, and perhaps better, commercial alternatives from the likes of Alesis and Lexicon if you're on a budget.

For example, the bottom of the line Alesis Nanoverb has a chorus/reverb combination setting. Currently under $84 Even less expensive is a similar FEX800 unit from Behringer. If I had $300 to spend, I'd opt for a Lexicon 400.
Adding reverb and chorus to these early digital instruments makes a big improvement in sound.