I just remembered this nifty little program I have on my computer that might be useful here. It is a tiny little downloadable program called NCH Tone Generator. It has something like a 30 day free trial period, but it only costs about $20 US. http://www.nch.com.au/tonegen/index.html -- Geoff Sykes -- Assoc. Los Angeles -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Philippe Errembault Sent: Monday, May 15, 2006 4:31 AM To: Cy Shuster; Pianotech List Subject: Re: online pitch source Hi all, With a computer, you have two possibilities, both can come from a file, so having the ressource on line will not help (except if you don't knowhow to download it on you computer). Only "usefull" online ressource I could imagine, would be a reference timebase like we use in the network time protocol. The problem with such a ressource, is that on the short term the delay introduced by the network will completely garbage it. This is only usefull to have a precise time of the day. Now, about the sound files themselves, In all cases, you will be depending on clock frequencies generated on you computer. Those clocks are generated by quartz which have a relatively good precision, but which will most probably be more precisely tuned for a time related clock than for a music related clock. now, I expect that electronic synthetisers will be relatively precisely tuned, or you would have a problem playing with more than one. I don't know, it might be the case...). Instead of using your computer, you have another option which is playing this from an MP3 (or alike) walkman (In this case, I the error will probaby be larger) you have two possibilities : Either you use recordings ("wave kind" files) or synthe "midi kind" files. The waves can be compressed (.mp3 files, .wma files, .ogg files, etc.) or not compressed (mostly .wav files). In both cases, waves are numeric samples supposed to be played at a certain speed (like on a CD). their precision will depend on the precision of the clock inside your wave player. In the case of compressed files, you have another problem with the quality of the file itself. according to the compression rate, the compression will more or less reshape your wave, in a way which is not related to your wave period. so the risk, is not only that you add harmonics to your wave, but that you add a slight modulation, which would add spurious frequencies around you center frequency. I have never tried to measure this so I don't know in which measure it can cause a problem for tuning. You can record you own waves, but it would probably more precise to build it by calculation (and optionnaly to chech it with you tuning fork). I built my own set of wave files according to the inharmonicity I measured on my piano. I put it on my MP3 player and tested my A440 against my fork, which shown a 1/2 Hz beat, which make an error around 2 cents. By the way, I found quite difficult to tune from this source, but since I'm no experienced tuner, this doesn't mean much. Another possibility, with a computer, is to use it's synthe, by piloting it with a midi file wich is HUGELY ;-) smaller than a wave. note that if your computer has a software synthe, you will get the same quality than with waves (with still the advantage of the smaller file. In this case, it might happen that you use another clock which could be more precise (this is higly hypothetic). The best option, would probably be to make a program which would measure the speed at which samples are eaten by the computers sound device, compare it with the system clock which is probably more precisely adjusted (a drift of 5 sec/day is equivalent to a 0.1 cents error), and automagically compensate the soundboard error by adjusting the waveform . Such a program probably needs to be written. Philippe Errembault ----- Original Message ----- From: "Cy Shuster" <cy at shusterpiano.com> To: "Pianotech List" <pianotech at ptg.org> Sent: Monday, May 15, 2006 1:22 AM Subject: Re: online pitch source > Might not an .MP3 audio file of an A440 tone be independent of network speed > or computer hardware? > > --Cy-- > > >
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