https://lmms.io/documentation/
I'm on LMMS 1.1.3
1) By placing an effect directly on the instrument, there is only this instrument that will be affected by this effect (and this allows you to save your instrument preset with its effects); by placing an effect in the mixer, several instruments can be affected by this effect. I think these are the only usefull differences for users.
2) If I'm not mistaken, the VOL knob of an instrument acts on the signal before this signal enters the FX tab of the instrument. In this FX tab, the signal goes through the effects from top to bottom. Then the signal comes out of the instrument, goes into the mixer's EFFECTS CHAIN (from top to bottom) and then goes into the mixer's volume fader. So, the different volume knobs/faders that you find in LMMS act at different stages of the signal processing chain.
2a) In most cases, in LMMS the volume is displayed in % (you can change this via Edit>Configuratiion>Display volume in dB). If I'm not mistaken, the volume levels (velocity) of the piano-roll are relative to the VOL knob of the instrument. So, if the velocity value of a note in the piano-roll = 200%, the volume of this note will be multiplied by 2 relative to the value of the VOL of the instrument.
Regarding the volume, I would say that the only thing that really matters is that the gauge of your mixer's master channel does not reach 200% or 6.02dB.
2b) When you assign an instrument to a mixer channel (e.g. channel 1), by default, the signal passing through that channel will be sent to the master channel (channel 1 SEND to channel 0). The SEND knob allows you to send the output of one channel to the input of another channel. To illustrate the interest of the thing, consider the following case: I have three instruments (Kick, Snare, Hat), I assign each one of these instrument to a channel (Kick = channel 2, Snare = Channel 3, Hat = Channel 4). The gauges of each of these channels allows me to see and compare their levels. What I want to do is compress and put a reverb on these drums. What I can do (one solution among others) is grouping my instruments: I send channels 2, 3 and 4 to channel 1 that I rename DRUMS (and I remove their SEND to the master channel). And in this DRUMS channel, I put a compressor and a reverb. I only used one instance of compression and one instance of reverb (it's practical, it's economical because I can also put a compressor and a reverb on each drums, and treating my instruments in a grouped way this allows me to obtain certain effects that are difficult to obtain if I treat my instruments separately). The gauge of the DRUMS channel allows me to check the combined levels of my three drums, and to compare it to the channels from which they come.
2c) There is only the master channel that really matters, its gauge must not reach 200% or +6dB.
2d) https://lmms.io/wiki/index.php?title=Using_MIDI (it's easier to give a link than to try to explain )
3)
W/D = Wet/Dry.
0: the effect is not applied (the initial signal is not altered), so 0=100% dry
From 0 to 1: the effect is gradually applied, with 1 = 100% wet.
From 0 to -1: for me, it's not clear, it's as if the value -1 reversed the parameter values of the effect.
DECAY and GATE. For me, it's not clear. I feel that this parameters are inoperative on many effects.
4) https://lmms.io/wiki/index.php?title=Controller_Rack
I'm on LMMS 1.1.3
1) By placing an effect directly on the instrument, there is only this instrument that will be affected by this effect (and this allows you to save your instrument preset with its effects); by placing an effect in the mixer, several instruments can be affected by this effect. I think these are the only usefull differences for users.
2) If I'm not mistaken, the VOL knob of an instrument acts on the signal before this signal enters the FX tab of the instrument. In this FX tab, the signal goes through the effects from top to bottom. Then the signal comes out of the instrument, goes into the mixer's EFFECTS CHAIN (from top to bottom) and then goes into the mixer's volume fader. So, the different volume knobs/faders that you find in LMMS act at different stages of the signal processing chain.
2a) In most cases, in LMMS the volume is displayed in % (you can change this via Edit>Configuratiion>Display volume in dB). If I'm not mistaken, the volume levels (velocity) of the piano-roll are relative to the VOL knob of the instrument. So, if the velocity value of a note in the piano-roll = 200%, the volume of this note will be multiplied by 2 relative to the value of the VOL of the instrument.
Regarding the volume, I would say that the only thing that really matters is that the gauge of your mixer's master channel does not reach 200% or 6.02dB.
2b) When you assign an instrument to a mixer channel (e.g. channel 1), by default, the signal passing through that channel will be sent to the master channel (channel 1 SEND to channel 0). The SEND knob allows you to send the output of one channel to the input of another channel. To illustrate the interest of the thing, consider the following case: I have three instruments (Kick, Snare, Hat), I assign each one of these instrument to a channel (Kick = channel 2, Snare = Channel 3, Hat = Channel 4). The gauges of each of these channels allows me to see and compare their levels. What I want to do is compress and put a reverb on these drums. What I can do (one solution among others) is grouping my instruments: I send channels 2, 3 and 4 to channel 1 that I rename DRUMS (and I remove their SEND to the master channel). And in this DRUMS channel, I put a compressor and a reverb. I only used one instance of compression and one instance of reverb (it's practical, it's economical because I can also put a compressor and a reverb on each drums, and treating my instruments in a grouped way this allows me to obtain certain effects that are difficult to obtain if I treat my instruments separately). The gauge of the DRUMS channel allows me to check the combined levels of my three drums, and to compare it to the channels from which they come.
2c) There is only the master channel that really matters, its gauge must not reach 200% or +6dB.
2d) https://lmms.io/wiki/index.php?title=Using_MIDI (it's easier to give a link than to try to explain )
3)
W/D = Wet/Dry.
0: the effect is not applied (the initial signal is not altered), so 0=100% dry
From 0 to 1: the effect is gradually applied, with 1 = 100% wet.
From 0 to -1: for me, it's not clear, it's as if the value -1 reversed the parameter values of the effect.
DECAY and GATE. For me, it's not clear. I feel that this parameters are inoperative on many effects.
4) https://lmms.io/wiki/index.php?title=Controller_Rack