MIDI to Pianocorder
By Will Dahlgren
In a message dated 95-06-05 00:06:44 EDT, you write:
> Subj: MIDI -> Pianocorder
> Date: 95-06-05 00:06:44 EDT
> From: mfontana@magnus.acs.ohio-state.edu (Mark Fontana)
> To: WillWiz@aol.com
>
>
> Hi,
>
> I just read the latest Automatic Music Digest with your discussion of
> the Pianocorder tape format. A few months ago, I was thinking about the
> possibility of writing a Standard MIDI file player that would encode
> Pianocorder tapes using a PC soundcard (Proaudio Spectrum, Soundblaster,
> etc).
>
> From your description of the format, it sounds quite possible, and I was
> wondering if you've already done something like this.
Yes, I have. The product is called the MC-2 and, is now sold by Bob Baker (708) 367-7996. Over the three years that I made them, about 100 MCs were sold .
The MC-2 is a two way interface. If you play a tape (or use their horrible keyswitch recording system), it will put out MIDI. Play MIDI in and it will put out a signal that tricks the Pianocorder playback board into thinking it is seeing a tape signal.
> If you'd want to provide an exact specification of what needs to go
> on the tape, I think I could do it.
Marantz published an installation and technical manual that originally sold for $75. You would want to find one of these. It's about 150 pages. If you want to pursue this project (and I am going to try to talk you out of it) I can give you a few phone numbers to try. Their system design IS incredibly clever. Remember, those guys didn't have any microprocessors around, It is all hardwired logic - counters; shift registers, etc. Quite frankly, I am in awe of their design. Also, they didn't have any storage oscilloscopes to collect data on what their circuits were doing! But then, how exactly did the inventors of radio know if THEIR circuits were doing anything at all?
About doing your project on a PC - I don't think it is possible. The signal on the tape encodes a 128 bit frame of 0s and 1s. Figuring out how to encode the frame is the easy part. The hard part is getting the timing and signal strength correct. The Pianocorder system is VERY fussy. In fact, their tape recorders have an azmuth adjustment on the head to aduust for signal strength. The basic timing for a bit must be 1/3500 sec. +/- about 10%.
Each bit is is encoded by changing the number of transitions during this 1/3500 sec. time. One transition is a 0 and two make a 1. The transition direction doesn't matter. Put another way, if you saw a 7 kHZ square wave, it would be all ones, while a 3.5 Khz signal would be all zeros. (I think??? - I am doing this from memory and I may have the details backwards.)
You can't write a PC program to do the above because the bios will jump out and do annoying things like update the system clock 18 or so times a second.
This destroys your perfect timing. I know, I tried! What you might be able to do is figure out how a .WAV file is encoded and try to translate MIDI to a .WAV file. If the PC cannot accurately play .WAV files, then music would sound off key.
Anyway, I have an idea that will save tou alot of time. Go out and take a second job at McDonalds. When you earn the $500 for an MC-2, you will probably have spent 1/10 the time it will take to do this. I spent about 5 months on the MC-2.
Now, all that said, if you already had a Pianocorder and were interested in this stuff for the hobby persuit, by all means go ahead. I will be glad to help you in any way I can.
> However, I don't have a Pianocorder system around at the moment. If I
> undertake this project, I would try and find a Vorsetzer model (any leads???)
> to experiment with. Do Pianocorder tapes run faster than standard cassettes
> (3.75 ips?); I seem to recall that they do.
Yes, the tape system does run at twice the speed of a standard cassette.. And, how about this, I do have a Vorsetzer I would love to sell you! Just send $$$ and pay no attention to the above paragraphs - it's a piece of cake.
> Any help or advice would be appreciated.
>
> Mark Fontana
>
>
> ps. This would be my first project with the Pianocorder system. Until now,
> I've been working on a system to optically scan 88-note rolls into MIDI files
> in real time. This project is done except for the usual tweaking associated
> with mechanical projects of this scale. The resulting MIDI files have a
> resolution of 400 ticks/sec, which is quite satisfactory (and probably
> overkill).
Would love to hear details about your roll reader system. I built a one-up 128 switch to MIDI system a couple of years ago, but never hooked it up to a tracker. Bob Baker has it now and he claims to have gotten it working by tying it into vacuum switches or something.
Will Dahlgren
CC: automatic-music@foxtail.com
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(Message sent Mon 5 Jun 1995, 16:11:52 GMT, from time zone GMT-0400.) |
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