Nuts and Volts - September 2017

Besides effects, entirely new ground-breaking musical instruments were developed during this time period including the analog synthesizer and the more obscure mellotron. The history of synthesizers is well documented in literature, but the mellotron — a unique beast indeed — seems to have been mostly forgotten over time.

You may now be asking yourself if you have ever heard the sound of a mellotron before, so I have prepared a short playlist (shown in Table 1) comprised of some of the most famous songs in which a mellotron was used.

If you are younger than 50, you may never have heard these songs before, but that’s an even better reason to check them out.

Being a consummate tinkerer, I have built just about every instrument/effect that has caught my attention over the years; some in hardware, some in software, and some using both. A couple of these projects have been published in Nuts & Volts, including: • “Building an Electric Guitar” in the June 2013 issue • “MIDI Buddy” in the February 2015 issue I also wrote a four-part series of articles for the now defunct Dr. Dobb’s Journal about creating electronic music components in software. If you’re interested in reading them, they are still available online at: • Part 1: http://drdobbs.com/java/229700113

• Part 2: http://drdobbs.com/java/230500178

• Part 3: http://drdobbs.com/java/231000557

• Part 4: http://drdobbs.com/java/231002076

Finally, I published a book about electronic musical effects in software called, “Digital Audio with Java,” published by Prentice-Hall (it’s now out of print).

One instrument I haven’t attempted to buy or build (until now) was a mellotron; although I have very much appreciated its use in progressive rock music. It’s possible to buy one these days, but the cost is prohibitive for an amateur musician like me.

This project began when I was reading a news group one evening and it mentioned that a mellotron digital sample set was available for free. I hadn’t thought about a mellotron in years, but this piqued my interest once again.

A week or two later, I was reading HackADay.com and it mentioned a Raspberry Pi sample player called

SamplerBox, available as open source code from a person named Joseph Ernest. The code (written in Python) had incredible specs — including 120 note polyphony — so, I immediately put the samples together with the sample player. The result is this project.

In this article, I will present a digital version of a mellotron based on the Raspberry Pi 3 and Joseph Ernest’s SamplerBox software that can be built relatively inexpensively. Check out Figure 1 for a cost comparison.

So, What Exactly is a Mellotron?

According to Wikipedia, “The Mellotron is an electro-mechanical polyphonic tape replay keyboard ... that works by pulling a section of magnetic tape across a head.”

Figure 2 shows a mellotron being played. These instruments typically have 35 keys, with each key coupled to a tape loop as shown in Figure 3. Thirty-five keys meant 35

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Table 1.

Group Song Link King Crimson The Court of the Crimson King https://www.youtube.com/watch?v=gvCmtHDDuu0

Moody Blues Tuesday Afternoon https://www.youtube.com/watch?v=GEMuAnFH_lM Beatles Strawberry Fields Forever https://www.youtube.com/watch?v=8UQK-UcRezE Genesis Watcher of the Skies https://www.youtube.com/watch?v=57Hic Yc Y4Ow David Bowie Space Oddity https://www.youtube.com/watch?v=i YYRH4apXDo Yes And You and I https://www.youtube.com/watch?v=H-rdL2Kkvz Y Rolling Stones 2000 Light Years from Home https://www.youtube.com/watch?v=wcy8o0gj-A0