Walkman Mellotron?

[untune]

No doubt everyone is familiar with the Melloman

http://www.mysterycircuits.com/melloman/melloman.html

I also found this little beast

http://blog.makezine.com/archive/2007/09/make_a_mellotron_out_of_w.html

I'm a big fan of tape and I think it's make a great lo-fi sampler... now it's gotten me thinking.  Would there be a way to take a cheap walkman and have JUST ONE with whatever you wanted on the tape, which could then be fed via some kind of simple analogue keyboard (resistors/trimmers for each note?) to create a monophonic lo-fi keyboard/sampler?

In my head I see a constantly playing/looping walkman, the output of the circuit is fed into a keyboard where each key acts as a switch, bridging the circuit as it went.  Anybody got any idea how it might work?  I've got a keyboard which would be pretty much perfect for the job, now the fun part is working out the feasibility of such a task

[Gordonjcp]

You could have a loop with a single sustained note, and use the keyboard and resistors to drive the motor speed controller.  I don't think it would stay in tune very well, and you'd have a fairly long portamento as the motor sped up and down.

I've got no idea how you could do percussive sounds; maybe use a stop foil and sensor so that when you triggered it, it would play the entire "sample".  If you were really ingenious you could make a similar kind of wire spring arrangement to a real Mellotron and use a solenoid to drive the pinch roller against the tape, after picking the right motor speed.

It's all getting a bit complicated...

[Timodon]

Wow. It's a cool idea... I see potential there. Not really sure how you'd make anything useful with just one walkman unless you could adjust the playback speed but 36 walkmen all loaded with different string samples could be interesting. Certainly cheaper than buying a mellotron.

[untune]

Haha yeah, the idea is to shoot for simplicity.  One walkman, with one tape (lets say a loop of approximately six seconds, I forget what the actual length of a tape loops is) outputting it's audio via the headphone out (could be modded for a better output I'm sure) and modded to loop constantly when the power to the circuit is on.

The tape would be a recording of a single sustained note.  The controls on some walkmans (volume, bass/treble boost) could even be utilised here.  The audio output would then have to be regulated (ie pitched to the correct note, let's say the middle C, assuming whatever is on the tape is always recorded at the correct pitch) via an analogue keyboard/switch setup.  Polyphony would need multiple tape players (well 13, enough to accomodate 25 seperate notes) but I'm not really fussed about that.  This can be the lo-fi mono synth version

The keyboard I'm thinking of is a 2 octave, I was inspired when I saw what this guy had done with the shell of his Memoplay:

http://haamu.com/soundlab.html

which is the shell I now have since the board is corroded.  I might yet be able to fix it but I like the idea of building something in the case as it's in great condition.  Make no mistake, I'd love to have a Soundlab to put in there but the cost/complexity of that project makes it a bit out of my league

His 6th and 7th photos down are of the original memoplay analogue keyboard.  Wires that are pushed into contact with bars.  Then from that he has made his own PCB to do the same.  I assume that his uses a gate/trigger/CV on the synth.  This would simply need a way to adjust the pitch of the sound output based on the key that is pressed.  Failing that, it would have to be 13 microcassette dictaphones and a lot of effort

Anybody got any ideas?

[untune]

Been thinking this over... I was thinking about this all wrong.  Just having different resistors for each key would do nothing... I forgot it needs to adjust the pitch of an audio signal, not an oscillator :S

Anyways... the tape motor idea.  It's technically do-able - it has been done using MIDI (with very poor range) and theres also a thing called Motorkeys (google it) whereby a guy has built a simple 1 octave keyboard that controls a motor using a very complex programmed circuit.

The other idea I had would be to use some kind of pitch shifting circuit.  I've looked into using a voice changer (if there was a pitch resistor, I guess that could be connected to the keyboard) but it would mean using a digital IC, and that would no doubt introduce some pretty nasty artifacts (low sample/bit rate and cheap ADC/DAC).  Very lo fi though, so perhaps not all bad.

The rest of my ideas are fairly mental, to be honest.  Seperate tape heads linked to individual keys, micro loops of tape glued around supply/takeup reels from inside cassettes arranged on a big motor-drive rotating bar.  It gets crazier   The original idea was to make it easy to have lo-fi samples stored on seperate tapes.  Rather than having to change 13 tapes, just change one

Is there any simple/efficient way to pitch shift in the analogue domain?

[Circuitbenders]

Have you seen the Chamberlain, the forerunner to the mellotron?

It had about 60 very long tape loops with a head for every key. Theres a section about it in the Mellodrama documentory but there also used to be some video here http://www.sonicstate.com/articles/article.cfm?id=101# but i can't get it to work.

[untune]

I think over the last few nights I've read about every single possible tape-based sampler, manufactured or DIY, ever made haha.

The Chamberlain looks ace, though I think I read there was some serious shock hazard on the inside?

Shame I can't seem to get that video to work either, but it certainly does look interesting!  It's a shame there's seemingly no way to compress this down to something portable, that uses a single tape... cheers for that link thoguh

I've been pondering the idea of motor control some more.  With some kind of direct drive walkman (well a DD walkman?) would it be possible to do 2 whole octaves?  An octave down is 1/2 and an octave up is 2x, if I'm not mistaken.  So technically having a constant C3 recorded on tape, being able to play the motor 2x the speed or 1/2 the speed would be sufficient?

How about hacking a walkman to be driven directly by a motor?  Any idea if any of these are feasible?

[electoyd]

sounds like a major headache for probably little end result,  though i do appreciate your creative enthusiasm! 

[jamiewoody]

hats off to anyone who takes on this ambitious project. i am totally impressed! too many moving parts for me. i would, however assume that this "mellotron" would work best with auto-reverse walkmans...

[untune]

sounds like a major headache for probably little end result,  though i do appreciate your creative enthusiasm! 

I think that sentence sums up pretty much everything I've ever done

In truth I've just dropped nearly 20 quid on a broken early 80s analogue keyboard and don't want to see such a cool and retro looking case going to waste!   I'm gonna get a refund though, just let them keep a bit for me keeping the keyboard.

My problem is that I can picture how ace it would look with a cassette tape revolving through a window in the top of it, and how cool the warbled old analogue sounds would be... it's just getting from A to B where the trouble starts

I've just managed to land a pair of identical micro reel to reel recorders for a tenner.  So a full on analogue tape delay will be in the works shortly

[Gordonjcp]

How hard would it be to "remake" an Optigan?

You'd need to work out a way of rotating an acetate disc at a fixed speed, and then work out a way to draw circular "film soundtrack" strips.  Print them off onto laser printer OHP acetate, then arrange an LED behind each track.  Would you need a photocell for each track?  I just don't know...

[jamiewoody]

hack a discman and burn a cd of samples? is that possible?

it seems like i read something, when cd players first came out, someone covered a cd with some kind of mack, and poked holes in it...play the cd and you hear weird randomness!

[untune]

@Gordon

I don't think remaking one would be incredibly difficult, however - the process of making some kiind of acetate disk might be.  I'm going to do some more research into the Optigan over the weekend.  A quick look on the site though reveals a service schematic for the optigan... that might even be handy for designing a keyboard aswell

http://www.optigan.com/content/tech/service-faq/

[Gordonjcp]

That's interesting, I hadn't read the service manual.

For the disc, I was thinking of some unholy mishmash of gnuplot and sox ;-)

[untune]

Gordon, if you're still reading this... I gather you've got some Arduino experience from doing some searching on the forum.  I've only come across it recently.  How difficult would it be to use an Arduino to either:

1) take the input from a keyboard and use it to change the speed of a motor, effectively pitching the sound up/down

2) run constant analogue audio output into it and somehow use keyboard-triggered DSP to pitch shift it in real time?