The sad saga of the BeatScope

Sometimes, technology is the answer to a question no one has asked.


A number of years ago I was working with a cover band. We were a four piece consisting of Guitar, Bass, Drums, and a Vocalist. A lot of the songs the singer wanted to do would require a little more instrumentation to sound right, so it was decided that we would experiment with adding some backing tracks.

I've never been a fan of playing to backing tracks. There is quite a lot that can go wrong.  

The classic example. The drummer starts the wrong track for the song and hilarity ensues!

In this White Zombie performance, the drummer can no longer hear the backing track once the band kicks in (0:37 Seconds) due to bad monitors. He drifts out of sync with the track and things go down hill from there. 

Usually the drummer will listen to a click track through headphones so he can keep in sync with the backing track. The rest of the band simply follows his lead. As you have seen, things go bad quickly if the drummer loses his place.

Now, one thing I could never understand is how drummers can listen to that click track blasting through their headphones (usually an obnoxious cowbell sample) for hours at a time and retain their hearing/sanity. And seeing the amount of Advil our drummer was swallowing after each rehearsal, I could see it was taking a toll.

I started thinking about other ways this could be accomplished. Then one night it came to me. Instead of an audio click track to keep tempo, how about a visual one!.  My mind started piecing things together and within a few hours I had planned out a device that was to be christened the "Beatscope".

My plan was to base it around a Motorola MC68HC705 Microcontroller for which I already had a development kit. I would record the backing tracks in stereo, pan the music to the right channel and send that to the main mixer for the audience. The left channel would contain DTMF tones (Dual-tone multi-frequency - You know, the ones that your touch tone phone makes when you dial it). Each numeric tone would represent a digit on the display. By syncing the tones with the backing tacks, the display would keep perfect time with the music. Genius!

I found a DTMF decoder chip called the TDK 75T202 and built the circuit to accept the tones and decode them to binary. This was then fed into the 65HC705 chip which in turn outputted the correct signals to light up the numbers in the display. Overall, not too complicated.

I wire wrapped a prototype and mounted it in a Brownie Pan (Yeah that's right!) covered with a plexiglass top. A gooseneck mic adaptor was attached to the back so it could be mounted on a mic stand. I proudly bundled it all up and headed for rehearsal, wondering what it will be like to accept my Nobel Prize for saving the hearing and last shred of sanity of drummers worldwide.

Brownie Pan FTW!

MC68HC705

TDK 75T202

Baby's got back!

The drummer tried it out and was immediately not happy. The one thing I did not take into account was how drummers need to look around the kit as they are pounding things. Eventually the drummer suggested I add a headphone jack and have it output a click that he could listen to. What's the point!!! I later tried it with another drummer with similar results.

If I was one of those highly driven individuals who don't know the meaning of the word failure, perhaps I could have continued refining the idea. But instead, I am generally lazy with a short attention span so the device now sits sadly in my pile of projects that might have been. Still, it was a great way to flex my digital design muscles and sometimes, it's all about the journey anyway.

If anyone is interested in trying this, I can post some schematics and code.