As you roll the low-pass filter gradually from the maximum treble position to the other extreme, it horizonally filters out first the upper treble, then (also) the middle treble, then (also) the lower treble, then (also) the upper mid-range, then (also) the middle mid-range, then (also) the lower mid-range, until you reach the other extreme, at which point your left with (mainly) the lows, which are passed by the filter -hence the term low-pass filter (as opposed to the other filter options on the superfilter -band-pass and high-pass.)
The Q is a boost; it follows the filter frequency; for example, if you turn on the Q at the extreme treble position, you'll get an upper treble boost -which some refer to as presence; if you turn the filter a little, THAT frequency (the upper treble) -which was just boosted- is now filtered out, and the middle treble is now boosted; turn the filter a little more, and THAT frequency is now cut, and the lower treble will be boosted by the Q; turn it a little more, and THAT frequency will now be cut by the filter, and the Q will boost the upper mid-range; turn it a little further, and the upper mid-range will be filtered out, and the Q will boost the middle mid range... and so on and so forth.
I don't think Skylarks have Q switches for their filters, do they?
Of course, this description applies to the Q when used with a low pass filter; I believe it would function in the reverse in the high-pass mode.
A minor point, but I believe the superfilter Q is spec'ed to a maximum 12 db, whereas the Series II instruments CVQs go up to 15 db. Of course, 12 dbs of Q should be more than enough; my custom Europas Q can go up to 12 dbs, but I rarely use it at maximum.
