Highly unusual, very little potential but tremendously charming. The noise of data, perhaps known to some as playing ‘software tapes’ in regular cassette players, in this case with the classic tape drive of the Commodore 64. Unorthodox put to ‘use’ by a music editor with a graphical interface. Martin Wendt aka Enthusi is responsible for the idea and programming. He made it in only 3 weeks and published it earlier this February.
Enthusi was so kind to give some insight information.
“When coding Tape composer I was of course inspired by the famous tool 1541 drive composer that used particular noises of the floppy drive to mimic music notes.
Since I always loved computer tapes and their drives – the infamous datasettes – I decided to try something similar on those.
The composer has an easy user interface displaying the current song the classic way: with simple graphic notes. I’m not much of a computer musician and always preferred sheet music over a tracker – also its vintage appearance met the overall idea of playing back music on an oldschool tape drive.
There are three methods to play back the edited song:
As sinus wave on SID – audible through the main audio output for testing mainly (who would want to use the sound chip for that anyway?).
Then of course two ways involving the datasette itself.
The datasette’s motor is powered by the c64 via the cassport. You can switch the power on or off by software (it will only start turning when you physically press play but you can power it independently). When you are used to loading tapes you may have noticed how the tape stops when the message FOUND PROGRAM appears and waits for you to press SPACE – this is achieved by cutting the drive’s power in between.
If you now switch the power on and off quickly in a loop the datasette begins to hum and buzz (some crunchers do so accidentally by shamefully ignoring the upper bits of $01).
By doing so pretty fast at specific frequencies you can pitch that noise to match (more or less) musical notes. So each note gets translated into a particular frequency to connect and disconnect the power to the datasette.
The duration of this cycle is of course given by the length of the note and its equivalent CIA-timer values.
The volume depends on the individual datasette but it was pretty hearable with all the drives I tested.
Inspired by this success I added another option to play back the music – this time recording it directly to a standard audio tape.
When saving programs to tape via datasette, the c64 encodes each bit into a series of pulses on the write line of the cassport. The signal is either on or off.
Maybe you once put a data tape into an audio tape deck and listened to it? Hopefully not to loud since all you get is inhuman tormenting noise…
But you can control this noise.
By setting the write line active (via the $01 zeropage address btw) for a defined time you can generate some sort of square pulse. The datasette automatically inverts every second signal so by producing two consecutive pulses you have generated some kind of rectangle wave form. A series of on, delay, off, delay, on, delay, off, delay creates a wave (approximately). By selecting suitable delays you can mimic audible frequencies matching your notes. The outcome can be listened to on any audio unit with speakers afterwards.
The example mp3 is such a recording of “the jungle book” theme. You will find some more songs on the disc image and maybe get your own catchy tune done in Tape Composer?…”