Brilliant Idea (Even If I do say so myself)

[Jaicen_solo]

Ok, I was looking at this yesterday and must admit to being completely blown away by the sounds this thing makes:
(Especially strawberry fields)
http://mysterycircuits.com/melloman/melloman.html

It occured to me that it may well be possible to create an entirely solid state, lo-fi mono mellotron using just a number of those ISD2560 recording chips and some clever addressing circuitry. Of course this is never going to be built, but surely it would be possible to have, at its simplest, a whole octave of short samples recorded to the chip (say 1x 60seconds of recording = slightly more than 8s per sample. ISD2560 has 10 addresses I think). If the chip was permanently set to looping playback mode, it could be possible to create an exclusive switching system such as the one i'm working on with R.G's help which will instantly recall one of the loops as long as the switch/key is pressed. If the loops were seamlessly recorded, they should endlessly loop quite nicely. Perhaps, a sample of silence should be looping permanently until a key is pressed.
To expand this system for more keys, more ISD chips can be multiplexed to increase the available recording time and addressing. Alternatively, extra chips could provide different sound sets, or be run in parallel for increased texture.
I'm sure there's a simpler way to achieve comparable results, but like I say, this was just an idea I had. I don't think it would be possible to make a multi-phonic device, but a DIY mono sampler keyboard would be brilliant! I guess it could be possible to use one chip for single notes, and another for chords and have a dual keyboard like a hammond
Oh dear, looks like i'm getting carried away here!

Am I insane, or is this actually workable? 

[smashinator]

Seems to me that it's possible, and could be kinda nifty.  I don't see why you wouldn't be able to make it polyphonic, you'd just need to run the various signals into a mixing circuit.

As you said, there's probably a much more elegant way to make your own sampling keyboard.  This one would give you crazy bragging rights though.

[Eb7+9]

I can supply Minshall reed organ samples // ... 8 seconds no looping is a good start

~jc

[Herr Masel]

Those sound samples make me want to cry, so pretty... Your idea sounds interesting, as does the melloman, I'm reading.

[cd]

LOL Oberheim beat you by around 20 years

Google for the Oberheim DMX, it was a drum machine that stored samples on EPROM chips.  Then there was a second machine called the Prommer which allowed you to burn your own EPROM chips to plug into the DMX.

[Dave_B]

I breadboarded a drum sample player about twenty years ago that's not too far removed from what you're decribing.  It used Simmons EPROMS for the sample storage.  I attached a set of four 74193 counter chips to the address lines of the EPROM, then clocked them with a 555.  The data lines were attached to a DAC chip and then to the final opamp.  It was fairly simple to build and fun to mess with.   

You could certainly add circuitry to record into memory chips (or Flash memory cards), but if I understand correctly, it sounds like you're talking about building a sampler.  Are you sure you want to get into that?   

[Peter Snowberg]

Beautiful!  

[Jaicen_solo]

I'm glad you guys agree this would be cool. I've been thinking it over and I realised that it would need to be made with two chips, as the 2560 has only 9 address pins, so for sharps and flats (total 12 notes I think) you'd require a second chip, unless one of the other series has more addresses.
I don't really want to get into EPROM's, as that's a whole other level of complexity, and it's not really analogue. Besides, I wouldn't know where to begin! I'm sure it would be easier to make something with a flash rom card and some microcontrollers, but if we always did what was easiest, then we'd all just buy these pedals.
The reason it can't be polyphonic is because the ISD series chips can only replay from one address at a time. It could be done using multiple ISD chips, but then how do you control which chip is playing what? Headaches ensue.
If I could design this, i'd have the chips be interchangable, so the addresses are all the same. THat way you can have a patch library. Maybe mount the chips to a 'cartridge' type device. I'd also want two keyboards like on a hammond, so that I could have chords playing from one, while I play a melody on the other. I think that'd be just grand with some old school samples recorded, especially if they have that sick wobbly feel of strawberry fields

[Jaicen_solo]

I've just been checking out the technical archives of the winbond site, looking for useful stuff this chip can do. Apparently, the addressing is actually handled by binary clocking, so it could actually be possible to have one chip cover one or more octaves. Coupled with some clever CMOS switches, it should easily be possible to create a mono-mellotron like keyboard.
I'm going to look into this a bit more 
Apparently, the chips can be used to construct sentences from words stored online. There are computer programs which can be used to load samples directly onto the chip like an EPROM. In that way, it would be quite easy to store a comprehensive library of samples, which can easily be loaded onto the chips. 

[Herr Masel]

Man that's genius! I would really like to help but I doubt there's anything I could contribute, anyway I'd build it for sure. But why couldn't you use one chip for each key, like the melloman has one walkman for each note? That way you would have lots of free addresses on the chip and could store 9 different types of sound on each chip, selectable with a rotary switch (either master or individual for each chip , that would even mean you could have a different sound for each hand).

[Dave_B]

The reason it can't be polyphonic is because the ISD series chips can only replay from one address at a time. It could be done using multiple ISD chips, but then how do you control which chip is playing what?

A microcontroller.   I bought a book from Paia about 20 years ago, Friendly stories about Computers and Synthesizers that explained that very idea, along with a lot of other "Build your own synth" related stuff. 

Dave

[Eric H]

But why couldn't you use one chip for each key, like the melloman has one walkman for each note? That way you would have lots of free addresses on the chip and could store 9 different types of sound on each chip, selectable with a rotary switch (either master or individual for each chip , that would even mean you could have a different sound for each hand).

Exactly. The brilliance of the Mellotron was partly due to its polyphonic abilities --when synths were mono.

BTW no one seems to have mentioned the skill of the guy that played those samples. That box will sound like a toy in the hands of most people 

-Eric

[Herr Masel]

I said the music almost made me cry. Well, you know. Anyway, so the whole deal should be pretty simple no? I have no idea what the pre and power amp stages should look like, as I don't know what kind of eq range and power synths need, but the melloman page gave same nice directions. One thing is for sure - I'm going to need to start learning to play the keyboards to justify this!

[Jaicen_solo]

Haha, I need to brush up my ivory twinkling too
If it's monophonic, that makes it much easier anyway. I was thinking i'd use it mostly for chordal accompaniment anyway, so I guess it's less an issue.
If money were no object, I would indeed use 12 ISD2560's, that would simplify a whole lot of things. Firstly, it would allow polyphony in exactly the same way as the Melloman, because each chip could be running simultaneously. Patch switching would also be a breeze. However, 12 chips = 1 Octave = £60 for the chips alone. I'm guessing the whole project would run to something like £100 (US$180 thereabouts). I think that's a little too much to be spending on a device like this
If I knew more about microcontrollers, I think this project would be a breeze. As it is, i'm not so sure! I'm still plucking up the courage to build the prototype of my looper!