Wurlitzer A200 EP phasing sound?

DSP, Plug-in and Host development discussion.
joshb
KVRist
81 posts since 13 Apr, 2016

Post Wed Aug 01, 2018 7:53 am

Can anyone explain the phasing sound heard when playing a key on a Wurlitzer electric piano? It's usually heard on multiple key presses and more obvious in lower octaves.

I know that it uses a reed as a resonator, unlike a Rhodes which uses a tine, but I'm pretty sure there's only one reed per key.

Any ideas?

JCJR
KVRAF
2345 posts since 17 Apr, 2005 from S.E. TN

Re: Wurlitzer A200 EP phasing sound?

Post Wed Aug 01, 2018 2:37 pm

I had real wurlies from about 1966 til maybe 1980, and repaired wurlies regularly afterward up to the late 1990's. My WILD GUESS is just "wild" unstable oscillating modes in the reed. I suppose they had as good quality control possible on the little steel reeds, and they are not exactly high tech. But every reed had a slightly different tone. And they costed a couple of bucks apiece. If you broke a reed and replaced it and tuned up the replacement and didn't like the tone, you either put up with the tone of the new reed or you spent another couple of bucks and try another reed hoping maybe the next one will sound more to your liking.

Imagine the reed is doing its simple "main" vibration mode, but other slower vibrating modes are chasing up and down the reed as it decays. I'm not explaining it well, but take a slinky or any random piece of spring steel and strike it in a dark room "stop motion" illuminated with a strobe light and you can see the vibrating modes chasing up and down the piece.

Rhodes tines were the same deal-- Each one had its own tone to a certain extent and some had more enharmonicity or "unstable vibrating modes" than others. So if you were a perfectionist who wanted every note to behave exactly the same you probably wouldn't be real happy with the instrument.

Acoustic piano strings are also thataway. Of course putting a new string in to replace a broken string, the new string is probably gonna be brighter, but say if you are restringing an entire piano-- The wound strings generally come cut to length but the unwound strings come on spools and you cut them off the spool while stringing the piano-- Some of the random pieces you cut off that long spool will have their own built-in phasing or "beats" after installation in the piano. If a note or two is so bad you can't stand it, just cut off a new piece of wire off the spool and hope it works out better next time.

The note-to-note variations are prized by some players, and generally if somebody gets busy trying to play a lot of notes then the variations don't get noticed unless it is drastic (or a person is easily distracted by such details).

joshb
KVRist
81 posts since 13 Apr, 2016

Re: Wurlitzer A200 EP phasing sound?

Post Wed Aug 01, 2018 8:24 pm

Interesting. I definitely wouldn't have thought of that.

So, is what you're saying that the reed vibrates at the main pitch, but it also "wobbles" for lack of a better word, because it's not a perfect tuning fork?

Now, how on earth to model such a thing?

Thanks for your thoughts!

JCJR
KVRAF
2345 posts since 17 Apr, 2005 from S.E. TN

Re: Wurlitzer A200 EP phasing sound?

Post Wed Aug 01, 2018 11:02 pm

I'm very ignorant of the topic, but so far as I know even tuning forks are not simple and intuitively obvious.
https://www.youtube.com/watch?v=m7xUtR2qevA

I think I recall hearing DX7 FM sounds that sound similar to the "phasing timbre evolution" of reeds and tines. Slightly out of tune modulators?

Just wild guessing, the different tones EPs sometimes make, holding sustain pedal and restriking a reed or tine, has to do with the restrike hitting the tine or reed "in mid-flight" causing it to take on a new vibrational mode?

An aside which may not be true, but I played wurlie and rhodes many years 6 night a week music gigs and broke my share of reeds and tines. It is so annoying to have to go thru a set or the rest of the night with an out of tune or absent note before you have time to fix it, one gets gunshy about trying to avoid breakage, and then when it happens again anyway, "Crap, broke another one. I wasn't playing it that hard dammit!"

I think broken tines and reeds had a higher probability of happening with re-strikes-- Hitting a tine or reed already in motion. Maybe tapping it the second time when the tine is in an "unlucky" position in its trajectory. Maybe that is silly BS but seems a lot of my broken tines and reeds happened right after fast double-taps. Maybe the hammer accidentally strikes the second time when the tine or reed is at its max velocity moving down toward the hammer?

The reed is fairly wide and flat and probably doesn't have much side-to-side motion. Maybe in some cases some torsional motion, dunno. The construction of the wurlie was such that it wasn't real convenient to look at the reeds while playing the instrument even with the instrument opened up.

Now rhodes tines, some of them could do weirder motions, or maybe it was just easier to observe their movement because of the construction of the instrument. A well-behaved tine would basically move up and down with the tone bar acting like one leg of a tuning fork and the tine acting like the other leg of the tuning fork. But "weird sounding" tines could have circular or figure-8 motions, or you strike the tine and it begins up and down movement then mutates to circular or diagonal movements and then mutates back to up and down movements.

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