QUOTE(madbassoonist @ Jun 8 2009, 07:33 AM)

I don't think my teacher meant perfect pitch, but it's quite hard to describe what he did mean - I think one example he gave was that you can tell the leading note because it feels like it's pulling up to the tonic. That wasn't worded very well, sorry!
I think this is fairly close to knowing the sound of all intervals above the tonic and knowing what the tonic is at all times. At Grade 6 your sight reading will be in a key so that could work OK.
Intervals from the previous note still work if the music is not in a key, which happens in some music written long before Schoenberg and Co. started making a habit of it. There is more work involved, because you need to be able to deal with many intervals that don't occur above the tonic in the major or minor scales, e.g. augmented fifths; diminished fourths; diminished and augmented thirds, sixths and sevenths. It's probably not worth memorising the more extreme examples, like the doubly diminished fourth that Elgar wrote in "Sing unto the Lord": you deal with the ones you can't hear directly by enharmonic conversions* until you recognise the interval, which works perfectly if you are singing with a piano tuned in equal temperament, and is a good first approximation (to be corrected by careful listening) in a choir that uses a more accurate tuning of consonances (good amateur choirs do this instinctively, and the best professional groups think very hard about it).
* Consider the interval from the mediant to the leading note in a minor scale, say C to G# in A minor. This is an augmented fifth, but is somewhat less forbidding if you replace the G# with Ab, whereupon the interval becomes the more familiar minor sixth.