Roland SP-404MK2 Reference Manual page 30

Using the Effects
You can also use pads [1]–[16] instead of the [VALUE] knob or the [CTRL 3] knob to select an effect.
To use pads [1]–[16] to select effects from #17 and up, hold down the [MFX] button and the [DJFX LOOPER] button at the same
time.
2. After selecting the effect, take your finger off the [MFX] button.
The effect turns on, and the effect edit screen appears.
3. Play back a sample.
4. Use the [CTRL 1]–[CTRL 3] knobs to adjust the parameters.
You can also access the effect sub-parameters by holding down the [VALUE] knob and operating the knobs.
30