Converting MIDI Performance to Player Piano Commands
By John Grant
In digest 95.11.29 Robbie Rhodes wrote, in part:
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Subject: Using Midi Editor for Adding Expression Coding
George Bogatko has introduced an interesting new subject (Re: Ampico-to-Midi in digest 951128).
But Whoops! Back up, George! In digest 95.11.26 I was talking about transferring music data to Midi for archiving, etc., and all-of-a-sudden you are talking about going the other way, from Midi performance into player piano commands. That's a much harder problem, and I don't know of any automated method available right now to do it.
[Snip}
The "tracker-bar clamp-on" seems prone to leaking, which is _deadly_ on a reproducing piano. A better method of hearing your editing progress would be with a set of "magnet valves" teed into the tracker-bar tubes under your Ampico piano. Use a set of Reisner vacuum valves controlled by the equipment described by Mike Ames in digest 951126. Be sure that the power supply (12 or 15 volts at 5 amperes) is well-filtered and regulated. You don't want the valve timing corrupted by hum or voltage sags due to crashing chords!
-- Robbie Rhodes
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I too have wrestled with the concept of a device which would slip over the tracker bar and electronically replace the paper. I even made some preliminary engineering drawings to accomplish this but have come to the conclusion that the most difficult nut to crack would be the fabrication of the gasket that would be needed between the tracker bar and its concave mating part. The selection of materials for this would be critical in that it would need to have some slight compressibility (as in an elastomer) yet be rigid enough hold the extremely fine "web" width between holes. My guess is that you could not do this with a die cut process as the force required to strip the material from the die would probably destroy the webs. Perhaps a laser machining process would be more successful. I believe the better approach would be similar to the CC-3 Cassette Converter manufactured in the '70's by "International Musical Industries", Santa Monica. [Come on Robbie, don't YOU know all about this? Fill us in.] My approach in my experimental system is to mount a bank of solenoid operated valves in a separate chassis (reversibly mounted) in front of or beneath a Duo-Art or Ampico stack, with a tube for each note or function connecting to a tee inserted into the hoses coming from the tracker bar.
Caution: The following may SOUND like, but is not intended to be, a commercial. In trying to come up with a suitable solenoid operated valve for this purpose, I first looked at the direct electric magnet valves used extensively in the pipe organ industry. While they are well suited for the function, they are fairly large, on the order of 5/8" x 1 7/8" x 2 1/4" for a small Riesner model I have. This is over 2 1/2 cubic inches before you add a valve seat and connector for the tubing. Their biggest advantage is they are relatively inexpensive, a reflection of the quantities in which they are made. I decided to make my own valve using a commercially available solenoid which is 3/8" square and about 1" long. I add a valve seat and tubing connector for a total length of 1 7/8", giving a volume displacement of approximately .26 cubic inch, almost 1/10th the size of the pipe organ magnets. Gang mounting the valves on a common aluminum rail (with necessary separation for cooling) increases the effective displacement to about .35 cu. in. per valve. In an effort to buy materials and components in reasonably efficient quantities, I offered to sell these valves to others who might be interested in them for similar applications. (Please see ad in July/August Amica Bulletin, p. 237.) While several sets were sold, the overall response was, well, underwhelming. Detecting that the interest may now be increasing, I am CONSIDERING "reopening the production line", again on a partially pre-paid subscription basis. I am putting together an e-mailable package on this which should be ready in a few days. If you are interested in receiving the detailed package, send me your email address with a request for it. Since it will contain some bit-mapped image files (viewable with a Windows accessory), I will only send it to those requesting it as it may take several minutes to download. I should be able to hold the maximum price at $8/valve but will probably not be able to get under $6/valve unless I get subscriptions for LARGE numbers. As I am in the process of switching ISP's, please send requests to: ir004161@interramp.com -John Grant
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(Message sent Thu 30 Nov 1995, 22:41:29 GMT, from time zone GMT-0500.) |
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