Thanks Dean! dp David M. Porritt, RPT dporritt at smu.edu -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Dean Reyburn Sent: Saturday, November 14, 2009 8:43 AM To: pianotech at ptg.org Subject: Re: [pianotech] ETD stretch vs pure (octaves) RCT's Octave Tuning Style (OTS) numbers 1 through 9 are simple to use, but they are not like a simple volume control, not at all. The numbers are a very high level representation of a complex, aural based tuning algorithm. RCT's tuning algorithm actually adapts itself to each piano as needed, without changing OTS numbers, but changing the OTS number will vary the stretch as needed. For example, OTS 4 (a middle of the road stretch which works on most pianos) targets a 4:2 octave plus about 1/3 bps between A3 and A4, and a 6:3 octave plus 1/4 bps between A2 and A3. However if the double octave A2-A4 is greater than 1 bps, then the two single will be squeezed in to fit. If too much squeezing is required (such as small, high inharmonicity pianos), RCT enforces a single octave minimum, effectively making the A2-A3 octave into a 4:2 octave. Tuning above A4 and below A2, RCT does it's best to use the same style as was required for that piano in the midrange. That's a simplification but you get the idea. Higher OTS numbers target more stretch, lower numbers less stretch. The user changes the stretch depending on the situation, piano, room, or whatever the tuner's or listener's ears require. RCT's OTS 1 attempts pure single octaves using the most prominent octave type (2:1, 4:2 etc...) for each part of the piano. OTS 7-8 will give you pure fifths and 12ths but with a controlled significant amount of beats in the octaves and double octaves. If the tuner wants to (for example) combine a one stretch in the midrange with another type of stretch in the bass or treble, RCT's Custom Equalizer tool lets the user adjust the stretch in each octave. Custom EQ uses octave type markers for 4:2, 6:3, 2:1, 4:1, 8:1 etc... for beat speeds readouts, the adjustment is done visually on a set of sliders that looks like a graphic equalizer. Hope that helps, -Dean Reyburn, RPT On Nov 13, 2009, at 5:48 PM, Porritt, David wrote: > Do these OTS numbers correspond to any partial scheme (i.e. 4:2, 6:3 etc.) or are they just numbers like on a volume control? > > dp > > > David M. Porritt, RPT > dporritt at smu.edu > > From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Rob Mitchell > Sent: Friday, November 13, 2009 3:49 PM > To: pianotech at ptg.org > Subject: Re: [pianotech] ETD stretch vs pure (octaves) > > This has long been a point of confusion for me. Smaller pianos typically have higher inharmonicity, requiring more stretch in the octaves in an attempt to match the higher partials. And yet on RCT, the higher OTS (Octave Tuning Styles) are recommended for bigger pianos. We had Karl Lieberman out a couple of weeks ago and I think he recommended using OTS 7 or 8 on Steinway D's. > > I'm assuming OTS 8 has more stretch in the octaves than say OTS 4. Do I have this backwards or am I missing something else? > > Rob > > Mitchell Piano Service > (415) 994-1030 > www.mitchellpianoservice.com > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ RPS, Inc. contact: <http://www.reyburn.com/contact.html> Dean Reyburn, RPT 2695 Indian Lakes Road web page: <http://www.reyburn.com/> Cedar Springs, Michigan, 49319 USA Sales & support: 1-888-SOFT-440 (or 616-340-7277) Fax: 616-696-8121
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