Available for Free

We are pleased to announce that as of the 3rd of March 2019 the RISC OS Sound Module RDSP 0.87 is now available for:

RDSP is now at release candidate 1 (v0.87). The latest version of the PDF manual is available here: See the news section for more information.

RDSP Tutorial Series

Episode 1 :

Episode 2 :

Example Sounds

RDSP supports recording its output to a WAV file. Some of the example programs have been used to produce the following recordings:

BBC Micro emulation BBC.WAV
Exclusive Or and Pulse Wave Modulation xor-pwm.wav
Game sound effects and room reverb room-effects.wav
Drum samples and room reverb drum-sample-added-reverb.WAV
Long envelope and delay amd hall reverb hall-envelope.wav


RISC OS originally provided 8 channel 8 bit audio based on voice generators which were implemented via loadable operating system modules. These modules could play back 8 bit digital samples.

Subsequently, this audio system was upgraded to 16 bit audio implemented via shared sound.

However, no simple API was provided to load and play sound samples. Also, no synthesis capabilites beyond the voice generators were implemented.

This is why AMCOG Games have developed RDSP.

RDSP provides a modern sound solution, that reflects an up-scaled, up-lifted traditional computer synthesiser chip in the form of a 'SOFTWARE SYNTHESISER'.

RDSP comes with full source code and implements:

  • 16 voice 16-bit 44khz audio channels
  • 4 waveforms that can be adjusted, combined and modulated to produce a wide range of tones over a near 8 octave range.
  • 16 bit sample loading and playback
  • Low-pass resonant filters
  • Integration with BASIC's SOUND and ENVELOPE commands
  • A digital delay effect
  • A digital chorus effect For further information on Chorus effects, please click here & scroll down to 'what is the chorus effect?'
  • A digital reverb effect with both hall and room settings
  • Recording RDSPs output to a wave file of up to 20 minutes in length
Demo programs have been included.

NOTE: RDSP is currently at release candidate 2 and full release is planned within the next few months.


RDSP has been tested on RISC OS 4 on Virtual Acorn and RISC OS 5 on Raspberry Pi 1,2 & 3 Beagleboard, Pandaboard, Cortex-A15 based systems, Titanium, ARM X6, RPCEmu and Virtual Acorn.

Please note that the BBC BASIC SOUND integration is not currently compatible with RISC OS 4.39


RDSP is free. It has also been included within the AMCOG Development Kit, please click Here for further information.

RDSP Features

  • NEW: As of version 0.86 : A reverb effect has been added
  • NEW: As of version 0.86 : Sound recording has been added
  • NEW: As of version 0.86 : A PDF manual has been added
  • NEW: As of version 0.40 : A chorus effect has been added
  • NEW: As of version 0.31 : Support for sound queuing for each channel.
  • NEW: As of version 0.26 : Support for stereo channel placement.
  • 16 sound channels
  • Waveform generation via phase accumlator oscillators that produce : Saw, Pulse-Wave-Modulation, Triangle, Pulse Noise as well as bitwise AND combinations of these waveforms.
  • Sample playback
  • XOR adjacent channel modulation to produce science fiction style and distorted sounds.
  • Just under an 8 octave frequency range
  • System wide 44khz 16 bit audio using shared sound
  • Sample and waveform modulation : Pitch, filter, amplitude and pulse width using a three stage envelope and ADSR envelope (1 per voice).
  • Digital delay effect
  • Integration with the SOUND and ENVELOPE commands
  • Partial legacy BBC Micro SOUND command compatibility
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