sweep the frequency control until they stand out more prominently. Do the same for the clarinets. If you find that the same center frequency works equally for both, skew one channel upwards in frequency and the other down. Now you have differentiated these instruments sufficiently for them not to mask each other.
Clarinet and trumpet - how to give each its own space in the frequency spectrum?
As a finesse, if you have two mid-range EQ sections per channel, or have enough computer processing power to run additional pug-ins, whatever frequencies you boosted on one channel, cut on the other, and vice versa. So not only are you making the trumpets more prominent at their key frequencies, you are scooping out a ‘hole’ in the same frequencies on the clarinet track. This technique is sometimes known as ‘complementary EQ’. It is a powerful tool.
When you are mixing a band like this, when you have either heard them play live in the studio, or it is a conventional line up and you know what it should sound like, always apply EQ in context. This means that you do not solo any channel while you EQ, apply EQ while all of the instruments are audible. In this way, you can see what effect the EQ has with reference to the entire mix. Many recordings are not made with conventional band instruments, or with the musicians not playing simultaneously. In cases like this, there is no reference point. You don’t know what it ‘should’ sound like. Rather than ‘live up to’ a standard, it is your responsibility to create that standard. This is more difficult, but it offers more creative opportunities too. In this case I will assume that you applied corrective EQ during the recording process, so all the instruments and voices sound fully adequate at least. You could try a faders-and-panpots mix, as in the whole-band example above, but the result will probably be something of a jumble. Since the instruments were recorded separately, there wasn’t much information to go on as to how they should blend. An Introduction to Equalization
Page 37