[T-Mobile Galaxy Note 4 Android Development] Lessaj:
Yea it's kernel level. In kernel/samsung/trlte/sound/soc/codecs/audience/es705.c I can see the function:

int es705_put_veq_block(int volume)

Which contains this section:

if (cmd > 0x9018000f)
cmd = 0x9018000f;

cmd = cpu_to_le32(cmd);
ret = es705->dev_write(es705, (char *)&cmd, 4);
dev_dbg(es705->dev, "%s(): write veq max gain 0x%08x to volume (%d)\n",
__func__, cmd, volume);
if (ret < 0) {
dev_err(es705->dev, "%s(): write veq max gain 0x%08x failed\n",
__func__, cmd);
goto EXIT;
}

/* VEQ Noise Estimate Adj */
cmd = 0xB0170025;
cmd = cpu_to_le32(cmd);
ret = es705->dev_write(es705, (char *)&cmd, 4);
if (ret < 0) {
dev_err(es705->dev, "%s(): write veq estimate adj 0x%08x failed\n",
__func__, cmd);
goto EXIT;
}

/* 0x00 ~ 0x1e(30dB) */
if (network_type == WIDE_BAND) {
if (extra_volume || es705->current_bwe)
cmd = veq_noise_estimate_adjs_extra_wb[veq_use_case][volume];
else
cmd = veq_noise_estimate_adjs_wb[veq_use_case][volume];
} else {
if (extra_volume || es705->current_bwe)
cmd = veq_noise_estimate_adjs_extra[veq_use_case][volume];
else
cmd = veq_noise_estimate_adjs_nb[veq_use_case][volume];
}

if (cmd > 0x9018001e)
cmd = 0x9018001e;

cmd = cpu_to_le32(cmd);
ret = es705->dev_write(es705, (char *)&cmd, 4);
dev_dbg(es705->dev, "%s(): write veq estimate adj 0x%08x to volume (%d)\n",
__func__, cmd, volume);
if (ret < 0) {
dev_err(es705->dev, "%s(): write veq estimate adj 0x%08x failed\n",
__func__, cmd);
goto EXIT;
}

/* VEQ Coefficients Filter */
if (network_type == WIDE_BAND) {
veq_coeff_size = 0x4A;
wdbp = (char *)&veq_coefficients_wb[veq_use_case][volume][0];
}
else {
veq_coeff_size = 0x3E;
wdbp = (char *)&veq_coefficients_nb[veq_use_case][volume][0];
}
cmd = 0x802f0000 | (veq_coeff_size & 0xffff);
cmd = cpu_to_le32(cmd);
ret = es705->dev_write(es705, (char *)&cmd, 4);
dev_dbg(es705->dev, "%s(): write veq coeff size 0x%08x\n",
__func__, cmd);
if (ret < 0) {
dev_err(es705->dev, "%s(): write veq coeff size 0x%08x failed\n",
__func__, cmd);
goto EXIT;
}

And to /proc/kmsg it's writing (on volume up):

<6>[ 1384.076591] [KEY] code(0x73), value(0)
<3>[ 1384.076615] sec_debug_check_crash_key code 115 value 0 state 0 enable 0
<7>[ 1384.105300] es70x-codec es704-codec-gen0: es705_put_veq_block(): write veq max gain 0x90180007 to volume (3)
<7>[ 1384.105676] es70x-codec es704-codec-gen0: es705_put_veq_block(): write veq estimate adj 0x90180014 to volume (3)
<7>[ 1384.105855] es70x-codec es704-codec-gen0: es705_put_veq_block(): write veq coeff size 0x802f003e
<6>[ 1384.131105] es70x-codec es704-codec-gen0: es705_put_veq_block(): success

<6>[ 1384.316625] [KEY] code(0x73), value(0)
<3>[ 1384.316635] sec_debug_check_crash_key code 115 value 0 state 0 enable 0
<7>[ 1384.333996] es70x-codec es704-codec-gen0: es705_put_veq_block(): write veq max gain 0x90180005 to volume (2)
<7>[ 1384.334436] es70x-codec es704-codec-gen0: es705_put_veq_block(): write veq estimate adj 0x90180014 to volume (2)
<7>[ 1384.334643] es70x-codec es704-codec-gen0: es705_put_veq_block(): write veq coeff size 0x802f003e
<6>[ 1384.361777] es70x-codec es704-codec-gen0: es705_put_veq_block(): success

So I think I've found the key, I merely need to unlock the gate...