Chiptune-esque sounds

Morshu · Post by **Morshu** » Tue Aug 30, 2011 8:45 pm

http://www.youtube.com/watch?v=UpZGqbiOAnU

i'm trying to make a chiptune like sound to play chords with like in the beginning of this song- but i find it hard to figure out what sort of sound wave and filters to use- as it never sounds close at all.- its decievingly simple sounding... but i can't get it. same goes for the square lead that goes over the constantly repeated chords.

im pretty sure its possible to recreate this, but ever since i've used synths, making amiga-chiptuney sounds has been difficult(unless its an arpeggiated sound)

btw- i'm not trying to merely copy the song, i'm just trying to figure out how to make chiptuney leads and chords etc. and if i knew how to play this ^ i would probably have a better understanding.

X-Trade · Post by **X-Trade** » Tue Aug 30, 2011 9:19 pm

Basically you only want to use square (50% pulse) and sawtooth waves.

Retro sound chips were decisively simple. Most didn't even have filters. Sample output and DSP could be emulated but only at a really low sample rate and by modulating the output of another oscillator.

Noise like you hear on the snare in that example would be generated digitally so have a low sample and bit rate - you could emulate that simply with the noise generator and decimator waveshaper - maybe a bit of lowpass filter.

Absolutely no resonance or EG on the filters.

one effect to produce more complex timbres would be via FM, although not the precise kind we know today. the control signal would be generated in software by the CPU so we're really only talking about a really fast (and actually quite slow compared to how high the Radias' LFOs go) LFO connected to pitch.

Similarly noise can be generated this way by modulating the pitch or amplitude of another waveform and using the random wave shape for the LFO.

contrary to popular belief, most of the sounds aren't actually generated digitally. A lot of these sound chips are basically an analog oscillator or two. In fact the best (and most popular at the time) chip was the SEM chip from the Comodore64 - and this was basically an entire analog synth on one chip, with three oscillators, a low pass filter, and level (envelope/etc) control.

the stepped nature and that comes typically from the limited CPU speed when controlling the chip. As envelopes and LFOs typically have to be modelled in the software, their output was noticeably quantised and stepped.

Morshu · Post by **Morshu** » Tue Aug 30, 2011 10:08 pm

so its more of a challenge of using the right effects and VPM/Decimator than anything else? I didnt quite understand the end of your post btw

X-Trade · Post by **X-Trade** » Tue Aug 30, 2011 10:33 pm

well, because the output levels, and oscillator pitches were done in the digital domain on the CPU (in program code), it was relatively slow. So things like envelopes and basically anything that controls pitch or amplitude, would come out relatively stepped or quantized. Unfortunately there isn't a proper Sample & Hold on the Radias/R3 so you can't really emulate that. And most don't bother anyway.

I never mentioned VPM. VPM might do something for you but generally it's too fast. I said to use a (relatively fast) LFO for pitch modulation. I say relatively fast because the LFO on our synths here go up to 100Hz whereas 'fast' for an LFO is typically 10-20Hz

This was all a list of ideas and research rather than a general direction.
I have several vintage computers lying around. In storage at the moment. But the important part is really that you're looking at very basic stuff - basic waveforms with pitch and amplitude modulation. Most didn't have filters, or only had one filter for all parts or only one oscillator. Decimator is mostly to be used to emulate early modulation based sampling effects e.g. on drums.

The decimator insert effect is a favourite of mine but for different stuff (I use it as a 'fuzz', reducing everything to 4-bit to make synth-metal chug sounds). but it does produce a nice interaction on the distortion on chords. I think its less 'authentic' and more mistakenly emulative - exaggerating the genre, but in a good way.

Morshu · Post by **Morshu** » Tue Aug 30, 2011 11:48 pm

i was able to create a pretty good patch that reminded me of amiga- but sounds far too rich to be such.

i'm suprised it only used one oscillator o.o btw play with the mod and pitch wheels on these two sounds(they are minor variations that sound a little different)- it makes it more authentic

http://www.sendspace.com/file/6jk81f

I think you will be pleasantly suprised with at least one of these.

copy the settings into your radias, its pretty great. simple nontheless though.

zalo · Post by **zalo** » Wed Aug 31, 2011 7:19 am

Also remember that most of the time the sounds are monophonic. A big part of the sound of chiptune/bit music is this fact. Instead of regular chords, they have to fake polyphony by using very fast arpeggiators.

Morshu · Post by **Morshu** » Wed Aug 31, 2011 8:24 pm

in this song its actually not doing that, but its making 3 monophonic sounds play at the same time on different notes so it is a chord. the 3 sounds are similar but slightly different. i analysed it after openning the .MOD file for it in modplug tracker.

Morshu · Post by **Morshu** » Sun Nov 13, 2011 12:47 pm

ive been able to get chiptune like sounds using your advice, but ive been unable to replicate the sound/s in that song. is cross mod going to help?

Timo · Post by **Timo** » Sun Nov 13, 2011 10:45 pm

PWM, multiplexing, wavetable drum kits, aaaah.

Long live the SID chip! And later Paula of course.

The chord-stabs you're hearing are samples. You can clearly hear the classic shortening of the sample as it's pitched up. The origin of the stab is likely from elsewhere (a real synth, sampled), rather than generated in realtime by a chip. The chord structure varies so it's not a single sample of a chord but it may be a single note layered (costly on channel usage), or more likely several short samples of different chord variations, re-used. For example one sampled minor chord and one major chord (or 5ths, 7ths etc.), used interchangably, transposing them up and down the keyboard as needed, rough and ready.

I can hear a drum track (crunchy lo-fi 8-bit samples, probably no more than 12KHz for those by the sound of it, lol, although the Amiga can use anything up to 28KHz), a bass track (literally a sawtooth transposed down several octaves), the chord stabs, and the square lead, giving four channels which is what the Amiga used. I'm pretty sure that song is from an Amiga as, apart from using samples, two of the channels are panned hard left and two hard right. Only reason I know is that it used to annoy the pants off me when I had my Amiga as I'm deaf in one ear and could only ever hear two channels (out of four) whenever I used headphones!

The stabs and lead sound like they have echo but it's merely achieved by triggering the same samples intertwined on other tracks using any spare slots available (multiplexing) and using volume changes to modulate them. It's a different effect to a simple delay as the 'delays' can of course each be pitched as they are effectively new notes, almost like an arpeggiated delay. It's really only something you can easily do by using a tracker. The stabs likely have LFO pitch modulation changes too, they have a nice little warble to them.

Morshu · Post by **Morshu** » Mon Nov 14, 2011 12:33 am

how can one get an authentic pwm effect from the r3? i've gotten close, but it sounds more 16 bit than 12 or 8. what is the best way to get the ULTIMATE pwm effect?

Timo · Post by **Timo** » Wed Nov 16, 2011 8:48 pm

To best emulate classic chip PWM you need to think back to both the parameters that were available and the given limitations of the chips, and really limit what you do. This is essential. This means:

• No ambient effects, or reverb or anything like that, you want it completely dry.
• Stick to using just one oscillator only.
• Strictly monophonic too, no polyphony here unless you're doubling up on other channels with other independent sounds.

The most classic sound is when the PWM is modulated. You can use a slow triangle LFO to try and achieve that characteristic "whine" as it reaches the very shortest pulse-width and passes through silence (100:0) before opening up the pulse again all the way through to square (50:50). Experiment with the LFO's waveshapes and contours to shape the modulation around the "whine".

Another technique is to use a one-shot EG to sweep the PWM downwards (in a downward sawtooth type fashion) on key-on. This is great for puncuating lead lines. Think Turrican 2 (C64 version), et al.

Modulate the pitch using LFOs for that retro type warbling vibrato. Make use of LFO fade-ins if possible, so it starts pure and then gently drifts into vibrato for effect.

Portamento is absolutely game on, there's plenty of portamento in classic chip PWM lines, it's switched on and off at will, accentuating certain notes.

You can double up lead lines on another oscillator, but use two, one-osc patches so they're independent. Transpose one up or down by one octave, and detune the lines for a thicker effect.

Try using oscillator sync and ring-mod too.

Set up fast arpeggiations to emulate "chords".

With making chip sounds it's all about wildy animating the modulation and sequencing, as there were no other gimmicks.

As you mentioned, synths still often sound too clean, so dirty it up with some bit-depth crushing, gentle distortion, waveshaping and drive. The original chips had distortion, glitches and noise all over them. That's what made them sound so great and characteristic.

Ironically you can do things on the C64 SID that you can't on modern synths. Like using one oscillator that's sequencing an arpeggio or other notes (audibly or inaudibly) while modulating another completely different audible oscillator, fading from one oscillator wavetable waveshape to another without needing two channels, programming wavetable sequences (although you can do this with the Radias to an extent by modulating the control value for the synth/drum PCM samples), using all three oscillators to modulate each other (using oscillator-sync and ring-mod) in a chain-reaction type waterfall fashion, LFO interlacing, wrapping the filter to re-appear at the opposite end of the spectrum if an LFO happened to push the value further than the maximum or minimum values at any one time, etc.

SanderXpander · Post by **SanderXpander** » Wed Nov 16, 2011 9:53 pm

I'm learning a lot here, thanks!

Morshu · Post by **Morshu** » Wed Nov 16, 2011 10:03 pm

this is quite interesting. please go on further into the depths of this subject, but how do you fade in an lfo's modulation? do you have to use the mod sequencer or something?
i've been doing something similar by setting the 3rd EG to lfo1freq

zalo · Post by **zalo** » Thu Nov 17, 2011 7:28 pm

Also remember that when using the Decimator, 8 bit games had 4 bit sound. Dialing it down to 4 bit will help you get closer.