Literature on sound waves, filters, envelopes etc?

snerkler

I've been flirting with dance music production for a while but in reality done very little. OK I did create a track (well remix) using Logic Pro 9 but it was very basic slicing, sampling and sequencing.

I've now taken the decision to stop playing about and learn it properly. I would like to go back to the fundamentals of learning how sounds are created, how these are affected by filters, what modulators do, what LFOs are, envelopes etc etc, preferably without too much physics. Ok so I realise that it's mainly physics but what I don't want is a load of baffling mathematical equations etc.

Does anyone know of any good books on this kind of thing, or source of good literature?

Any help appreciated.

P.S. I've always loved the Roland TB-303 but they're too expensive for me so am looking at the TB-03, or Cyclone TT-303. Does anyone have experience of using both and can say which has the better Acid 'squelchy' sound? Also, apart from the looks are there any disadvantages of the Cyclone TT-303 Mk2 over the original as I'm struggling to find any of the originals in the UK.

ubrain

I'm glad you realise 303 rulez!
I worked in dance music throughout the nineties.
Early on, once I'd realised that 'the sound' I was always struggling to make right was actually the 303, I always used the real thing - at one point I had 4 of them It's a decade since I checked any of the copies out but up to that point, definitely, they were all pants. Maybe something's come along since... dunno!

Happy to give you a brief overview of some basics to get you started. It's tricky to know where to start though as (and I don't mean to sound patronising) I don't know how little you know.

I trust you know what a sine wave is?
Do you know how a sine sounds different from a sawtooth or triangle wave?
Do you know what a square wave sounds like?
Do you know why they sound different to each other?

You're familiar with what's meant by frequency and how that differs from amplitude?
Do you know what high-pass, low-pass and band-pass filters are? And how applying one to the various wave forms above affects the sound you hear from each?

snerkler

The newer clones definitely sound close imo.

Thanks for the pointers, much appreciated. As you can see from my answers above I have a lot to learn. I shall google these over the weekend, but this was exactly the kind of literature/info I was after and when I looked before I couldn't find a good source.

ubrain

Here are some basics - I'll keep the science to a minimum. Funnily enough, some of my best stuff was made before I knew any of this. Because I didn't have a clue what I was actually doing, all I could do was listen to the noises coming out and use them accordingly. Listening is the most important fundamental

WAVEFORMS
A sine wave is a pure frequency. The note you hear, the 'fundamental frequency', is all there is to it. It is the simplest, cleanest tone, the building block of all other tones and in a musical sense, pretty boring really.

Now, while the fundamental gives us the note we perceive, one instrument playing a C sounds very different from another playing the same note. This is because all sounds (other than a sine) are made up of various frequencies, at various relative amplitudes, all interacting with each other to create what we perceive to be the character or 'timbre' of the sound.

Take a pure sine and add another, at twice its frequency and half it's amplitude. This is called a harmonic. Specifically, the 2nd harmonic. The 3rd harmonic is the fundamental frequency x3 at 1/3 the amplitude. The 4th at 4x the fundamental 1/4 amplitude and so on...
A sawtooth has all these harmonics present while a square has only the odd harmonics present. Hence they have different characters to each other.

OK, that's the 'why' so now listen to the 'what':

Here's a vid that demos the sine, square and saw waves.
                                Here's another that includes a triangle wave.
                               
This vid is a good demonstration of how particular sets of sine waves added together combine to make up other waves.
                               
FILTERS
A filter, cuts out certain frequencies. A high-pass cuts out low freqs while a low pass cuts out high freqs. Band pass, cuts out both, letting through a 'band' of frequencies. This is where the sine proves itself to be totally boring as, applied to a sine wave, a filter either lets it through, or doesn't - there's no middle ground. Any other tone will have a mix of frequencies for the filter to act upon, so changing the nature of the sound gradually to make new sounds.
The character of a filter is determined by stuff like:
- Its slope ie. the rate at which it attenuates on the other side of it's cutoff frequency.
- Resonance is an accentuation around the cutoff frequency - and is the fundamental source of the acid experience!

OSCILLATORS & LFO's
An oscillator osculates - it goes up and down. If it goes up and down fast enough it produces a frequency that we can hear. The manner in which it goes up and down determines the timbre of that sound eg. Sine, saw, square etc.
If it goes up and down at a frequency below that which we can hear, it's called a Low Frequency Oscillator or LFO and we use this to make other stuff go up and down. We might apply this LFO to modulate the amplitude or frequency of an audible wave, we might apply it to the cut-off point of a filter. We might apply an LFO to the frequency or amplitude of another LFO which is controlling another LFO which is changing the brightness of a particular light on the mixer but if we did that, it's a sure sign we're too stoned and it's time to go to bed.

ADSR - Envelope shapers
So far we've looked at constant cycling 'states of sound' but to make things even more interesting, in so-called real life these various frequencies change over time giving us all sorts of clues as to what we're hearing.
A good example would be the pluck of a guitar string. The frequency it ends up resonating at is determined by its length, thickness and the tension on the string. However the act of plucking it increases the tension momentarily and so increases the pitch momentarily. There's also an amplitude peak as the string is plucked. Then, very quickly, it settles down to oscillating at its note where it remains pretty much until it is stopped/damped.
ADSR stands for Attack, Decay, Sustain, Release which are the 4 stages of a basic envelope.
Attack is the time it takes to reach the initial peak of the sound. Decay is the rate it drops off from this initial peak. Sustain is the level the sound rests at (this is where we typically ascertain the note of it) and Release is the time it takes to drop away from the sustain level to silence.
As you play a note, this ADSR process is triggered giving shape to the note. The aspect of the sound that it's applied to though could be the frequency, amplitude, the cut-off of a filter - in each case producing an entirely different nature of instrument note.


I hope that all helps you get moving - obviously there's a lot more to be said but I have to go do some work at some point ;-)
I recommend hours, days, months, years of noodling... and listening!

snerkler

Wow, thanks very much for all of this it's very much appreciated. I don't have time to read it at the moment but will certainly go through it at the weekend

snerkler

Finally got around to reading and watching this, really great stuff and very helpful. I particularly liked the last video and also the info on LFO's and Envelope shapers. I still don't fully get LFOs though so I need to look into this more.

Thanks for the help, given me somewhere to start and then allow me delve deeper

One question, on the 303 there's an envelope modulator knob, what is this. I understand the paragraph about how cut off, decay etc affect the sound, but not what the env mod does.

ubrain

OK, first the LFO thing.
An oscillator, by definition, goes up and down. If it goes up and down more than about 20 times per second (and less than about 22,000 times per second), we can hear it as sound. If it goes up and down slower than that, we can't hear it and so it is referred to as a Low Frequency Oscillator. We use these to control other stuff.

For example -
Say you have an oscillator (O1) making a triangle wave of 440hz. It is in effect, 'buzzing in the note of middle A'.

If you apply an LFO creating a saw wave at 0.5hz, to the frequency of O1, O1's pitch will slide down from a higher note to a lower note over the course of 2 seconds then step up to the high one and repeat. To use a fairly typical analogue standard, if the amplitude of the LFO was 2v, O1 would start at 880hz, slide down to 220hz and repeat. Musically this would be, in effect, a glissando from the A above middle (A4), 2 octaves down to the A below middle (A2).
If you applied the LFO as a square wave at 2hz, to the frequency of O1, it's pitch will step between  A4 and A2, cycling twice per second. In effect you'll be hearing 4 notes per second that would sound like eighths, alternating between A4 and A2 at 120bpm.

Alternatively -
Say you apply a low pass filter to O1. You stand there twiddling the knob up and down to create wonderful sweeps of frequency.... until your fingers get a bit achey.
So apply the LFO to the cutoff frequency of the filter and it will wave it up and down for you. A sine will give a smooth up and down sweep, a saw will open it up then sweep down cutting out frequencies as it goes. A reverse saw will start low and sweep up, the sound getting brighter and brighter until the wave of the LFO steps down again.

Similarly LFO could be applied to the amplitude (volume).

The 303 thing
One of the elements that defines its character, the 303 has a preset envelope shape wrt ADS (and a knob to vary Release time). The env mod knob varies the depth of this envelope. The envelope is applied to both amplitude and filter cutoff.
Further, you can program accents onto individual notes which affect the depth of the envelope too and there's a further knob to control the extent that the accent affects the envelope.

snerkler

Thanks very much again, it's starting to make a lot more sense now

Following the discussion it would seem wrong not to post this old classic

                               
I would love to know how they created the sound of the main 'melody'.

ubrain

Classic!
Are you talking about the main bassline or the more screechy rave sound?

snerkler

The sort of screechy/tweety sound, basically the first sound you hear (not the spacey synth sound)