If you already have a Mother 32 - and I guess you love it - and you think about getting modules - I fear for your wallet - in a long term view 
If you tend not to be the absolute disciplined person, or suffer a little under GAS, be prepared that a small case to swap modules will be more of a beginning and evolving love, rather than a long term lasting solution.
Maybe you will end up like some of us ā¦ but itās worth every cent 
The Machinedrum has 16 channels that you can set so that they play a sine wave. I decided to try to do some kind of additive synthesis with it yesterday night.
Real fun ! I tried different pitch/decay/panning/reverb/delay/volume settings and random trigs, then LFO on pitch, I got some very interesting resultsā¦
I also played a bit with the amplitude modulation to bring other frequenciesā¦ Distorsion and SRR would mainly bring to much dirt on the sound for my taste.
I also played with the EQ frequency, removing some of the spectreā¦
(I 
)
I still have to experiment, I look forward sampling a phrase and get crazy with thisā¦ Not sure how I can actually PLAY this as a synthā¦ I have ideas to go towards this direction with the Monomachine, should be easierā¦ After all, using ENS with sine wave I should get up to 18 waves !
And I have to read some theory to come up with new ideas. But so far, much fun !
Killed the GAS for modules pretty good 
You are not going to get much from braids as the monomachine stomps it , in terms of sound
At one point I Had the morphing e50, mn dpo running together and thought the mono sounded better
Now a full buchla thatās a different story - itās wild and organic
Maybe I should just use the wide Mono offer in terms of oscillators through A4 !
Thank you @Orwell for killing another time the fake need for modules 
So I tried to do some additive like synthesis with the Monomachine tonightā¦
Not as good as MD : I found the Sine waves not as precise as in the MD, the sound is blurry as hellā¦
A pity : with the ENS chords I would be able to actually play 4 sine waves per track. And the cascaded tracks made it possible to play with the sum of them quite easilyā¦
Such a pity the sound is not there ! I might have overlooked something, any idea guys why the Mono would sound not as precise as the MD ?
I didnāt know I didnāt know that much !
whole lotta synth in this world
That link just gave me some serious head spin.
Mixing analog sounds is subtractive by necessity; you must make room for a bouquet of instruments to fit withing the range of audible sound. Trees which are pruned (branches cut) grow bigger and bear more fruit.
I have the equivalent of 18 oscillators in my kit. I rarely use them all. Five of them are Moog and the others are Elektron. The majority are used for percussive sounds. Is that additive synthesis?
I think ADSR modulations can never be over emphasized in creating a sound. Subtractive synthesis is just another way to emphasize a frequency (half empty; half full). There would be no emergence of rhythm with out subtractive modulation of levels.
Not exactly, but sorta.
Basic additive has you picking a selection of sine waves at ratios of a fundamental (often harmonic, but could be aharmonic). You then vary their intensity over time, so some harmonics come in or out at different speeds, to shape the tonal character in fine detail over time.
Bash a piano key really hard and youāll hear its colour change at different rates in different parts of the spectrum ātil itās all decayed. Additive helps you do that.
But then you can go wild with it.