Chords for Inside a Mellotron M400: How the Mellotron Works

Tempo:
115.2 bpm
Chords used:

C

C#

F#

D#

C#m

Tuning:Standard Tuning (EADGBE)Capo:+0fret
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Inside a Mellotron M400: How the Mellotron Works chords
Start Jamming...
[F#] [C#m]
[D#m]
Hi, I'm [G#] Allison from Beltone Synthworks, and I'm going [D#] to tell you a little bit about how
the Mellotron M400 works.
So this is a Mellotron I just finished restoring.
It was made [C] in 1976.
The Mellotron is a totally unique [D#] instrument in which every key plays back an actual recording
of that note from a strip of magnetic tape.
There are 35 keys, so there are 35 strips of tape and 35 individual play heads.
And each set of Mellotron tapes has three different sounds on it that you can select
between using this sound selector switch.
So this is the original set that I believe it came from the factory with, and the sounds
it has are flute, [F#]
[C] violin.
[F#] [E]
[C] [F#]
[C#m] [F#] [D#] So I'm just going to show you the parts of the Mellotron and explain a little bit about
how it works and what they all [C#] do.
Okay, so we're going to start out by looking at the back of the instrument and just sort
of explaining what the parts are from the bottom up.
So inside this box is the power supply.
You can't [C] really see it, but it's pretty simple, but it delivers a variety of [C#] voltages to different areas.
There are two main things that have to be done in here when you work on a Mellotron.
The first thing is replacing all of the [C] electrolytic capacitors in here, and the second is correcting
[C#] a ground loop, which has been designed into the instrument with the way the capacitors are wired.
So that's something that you can do that will substantially decrease the 60 Hz hum on the output.
So this right here is the motor.
It's a pretty heavy-duty motor, and you can hear it's fairly loud.
And what it does is it turns the capstan that is used to advance the tapes.
It has to be pretty strong because it has to be able to continue to maintain a consistent
speed while being subjected to the friction of having several tapes pressed against it.
[N] So just to show you the very simple and sort of limited electronic aspects of the instrument,
this is the motor control board.
Now this one still has what's called a CMC-10 board in it, which is the original board used
by the M400.
But a lot of people now opt to replace this entire board with a new board that you can
get from Mellotronics.
I did my best to shore up this board to make it work as well as possible because that's
what the client wanted.
So I gave it a full recap, replaced all the electrolytic capacitors, and replaced the
power transistors, and then did something to bridge a couple of very tenuously connected
power rails in there, which were one of just many ways in which there are sort of sketchy design decisions.
In addition, there are also some serious ground loops designed into the instrument, but that's
a story for another time.
But over here, this is just the basic tone and volume and pitch controls.
This actually just operates a little lever that shifts the entire playhead frame to allow
it to be aligned with different parts of the tape.
So each tape strip has three sounds on it, and they're just side by side in a row, and
what determines which sounds you hear is just how they're aligned over the playhead.
So this is just a very crude mechanical control to allow you to switch sounds.
And if you put it in between, you get to hear a blend of the two sounds at once.
[Fm] So let me show you what happened from this perspective when you [C#] press a key and have
a [C] note playing.
So here, these are all the strips of tape, and each one of these is five feet long approximately,
and they're [C#] not loops, they're just strips, and each is connected by a spring down here
to the bottom of the frame at the lower part of the instrument.
[C] So when you press a note and the pinch roller starts advancing the tape against the capstan,
it just pulls it up.
[F#]
[C#]
And when it [C] runs out of tape, it'll just stop.
And then you let [C#] go, and it just gets pulled right back down by the spring.
[C]
Okay, so the way you see the keys popped up, [C#] that normally wouldn't happen.
[C] It's just because I took the rod that [Cm] holds them down away for the sake of this demonstration.
But basically what happens [C] is that this spinning flywheel here, which is connected to the motor
via this rubber belt, just like a turntable, is spinning this wide metal rod called a capstan,
which goes across the width of the entire keyboard.
[C#] So when you press [Cm] down a key, there are two things that happen.
So this is a key that I took out from this slot right here.
This freely spinning wheel here on the key, called the pinch roller, pushes the tape,
which is, this is the tape, you can see that's one of the strips of tape, pushes it down
against the capstan, which makes it start moving, advancing.
And the other thing that happens is that this screw right here [C#] presses down this pinch roller
to pin the tape against the playhead, which allows you to actually hear it.
And all these screws, [Cm] and as well as the tension of the key itself, and [C] the alignment of this
presser pad tab have to be perfectly lined up for it all to work.
[C#] [F#]
[C#m]
[D#m] [F#m]
[D#m] So even after everything is perfectly adjusted, you'll always have notes that sound a little
different from the others, or might even be out of tune.
And that's just part of the distinctive Mellotron sound.
There's nothing else like it, and once you know what [G#] it sounds like, you start recognizing
it on a lot of recordings from the 1970s.
So thanks so much for watching.
I hope you sort of understand how a Mellotron works now.
[D] And if you want to read [D#] more about what I do, and just synth repair tips and synth repair
experiences, you can check out my
Key:  
C
3211
C#
12341114
F#
134211112
D#
12341116
C#m
13421114
C
3211
C#
12341114
F#
134211112
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[F#] _ _ _ _ _ [C#m] _ _ _
_ [D#m] _ _ _ _ _ _
Hi, I'm [G#] Allison from Beltone Synthworks, and I'm going [D#] to tell you a little bit about how
the Mellotron M400 works. _
So this is a Mellotron I just finished restoring.
It was made [C] in 1976.
_ The Mellotron is a totally unique [D#] instrument in which every key plays back an actual recording
of that note from a strip of magnetic tape.
There are 35 keys, so there are 35 strips of tape and 35 individual play heads.
And each set of Mellotron tapes has three different sounds on it that you can select
between using this sound selector switch.
So this is the original set that I believe it came from the factory with, and the sounds
it has are flute, [F#] _ _ _
_ _ _ [C] violin.
_ [F#] _ [E] _
_ [C] _ _ _ _ _ _ [F#] _
_ [C#m] _ _ [F#] _ _ [D#] So I'm just going to show you the parts of the Mellotron and explain a little bit about
how it works and what they all [C#] do.
Okay, so we're going to start out by looking at the back of the instrument and just sort
of explaining what the parts are from the bottom up.
So inside this box is the power supply.
You can't [C] really see it, but it's pretty simple, but it delivers a variety of [C#] voltages to different areas.
There are two main things that have to be done in here when you work on a Mellotron.
The first thing is replacing all of the [C] electrolytic capacitors in here, and the second is correcting
[C#] a ground loop, which has been designed into the instrument with the way the capacitors are wired.
So that's something that you can do that will substantially decrease the 60 Hz hum on the output.
_ So this right here is the motor.
It's a pretty _ _ heavy-duty motor, and you can hear it's fairly loud.
_ And what it does is it turns the capstan that is used to advance the tapes.
It has to be pretty strong because it has to be able to continue to maintain a consistent
speed while being subjected to the friction of having several tapes pressed against it.
_ [N] _ So just to show you the very simple and sort of limited electronic aspects of the instrument,
this is the motor control board.
Now this one still has what's called a CMC-10 board in it, which is the original board used
by the M400.
But a lot of people now opt to replace this entire board with a new board that you can
get from Mellotronics. _ _
_ I did my best to shore up this board to make it work as well as possible because that's
what the client wanted.
So I gave it a full recap, replaced all the electrolytic capacitors, _ and replaced the
power transistors, and then did something to _ bridge a couple of very tenuously connected
power rails in there, which were one of just many ways in which there are sort of sketchy design decisions.
In addition, there are also some serious ground loops designed into the instrument, but that's
a story for another time.
_ _ _ But over here, this is just the basic tone and volume and pitch controls.
_ This actually just operates a little lever that shifts _ the entire _ playhead frame to allow
it to be aligned with different parts of the tape.
So each tape strip has three sounds on it, and they're just side by side in a row, and
what determines which sounds you hear is just how they're aligned over the playhead.
So this is just a very crude mechanical control to allow you to switch sounds.
And if you put it in between, you get to hear a blend of the two sounds at once.
[Fm] So let me show you what happened from this perspective when you [C#] press a key and have
a [C] note playing.
So here, these are all the strips of tape, and each one of these is five feet long approximately,
and they're [C#] not loops, they're just strips, and each is connected by a spring down here
to the bottom of the frame at the lower part of the instrument.
_ _ [C] So when you press a note and the pinch roller starts advancing the tape against the capstan,
_ it just pulls it up.
[F#] _ _
_ _ _ _ _ [C#] _ _
And when it [C] runs out of tape, it'll just stop.
And then you let [C#] go, and it just gets pulled right back down by the spring.
_ [C] _ _ _
_ _ _ _ _ _ Okay, so the way you see the keys popped up, [C#] that normally wouldn't happen.
[C] It's just because I took the rod that [Cm] holds them down away for the sake of this demonstration.
But basically what happens [C] is that this spinning flywheel here, which is connected to the motor
via this rubber belt, just like a turntable, is spinning this wide metal rod called a capstan,
which goes across the width of the entire keyboard.
_ _ _ _ _ [C#] So when you press [Cm] down a key, there are two things that happen.
So this is a key that I took out from this slot right here.
This freely spinning _ wheel here on the key, called the pinch roller, pushes the tape,
which is, this is the tape, you can see that's one of the strips of tape, pushes it down
against the capstan, which makes it start moving, advancing.
And the other thing that happens is that this screw right here [C#] presses down this _ pinch roller
to pin the tape against the playhead, which allows you to actually hear it. _
And all these screws, [Cm] and as well as the tension of the key itself, and [C] the alignment _ of this _
presser pad tab have to be perfectly lined up for it all to work.
[C#] _ _ _ _ [F#] _ _
_ _ _ [C#m] _ _ _ _ _
[D#m] _ _ _ _ _ [F#m] _ _ _
_ _ [D#m] _ So _ even after everything is perfectly adjusted, you'll always have notes that sound a little
different from the others, or might even be out of tune.
And that's just part of the distinctive Mellotron sound. _ _
There's nothing else like it, and once you know what [G#] it sounds like, you start recognizing
it on a lot of recordings from the 1970s. _
_ So thanks so much for watching.
I hope you sort of understand how a Mellotron works now.
[D] And if you want to read [D#] more about what I do, and just synth repair tips and synth repair
experiences, you can check out my

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