That's interesting, I agree that transients are not limited to attack, but I would also say that attack isn't just limited to transients either. Here's my take: Transient response, for me, is a more "technical" characteristic of a transducer or an amp. A transient I take to be any part of the sound which is of short duration (a few ms or less), and good transient response is about reproducing those accurately (so it's typically correlated with speed). Because a transient is short, it involves a lot of high-frequency components, so good transient response probably necessitates no ringing or anything like that. Commonly transients occur at the leading edge of some sound - the start of a trumpet note, the ting of a triangle, the strum of a plectrum over guitar strings. But transients can also occur at the end of a sound as well, like if you stop a woodwind instrument with your tongue or damp guitar strings with your hands. Pure transients turn up in certain kinds of electronic music (Alva Noto, Ryoji Ikeda, CoH, SND, most things on Mille Plateaux, anything called "clicks and cuts"). "Attack" on the other hand, I see as a combination of various other features which are to do with the convincing reproduction of the start phase of a sound. Transient response plays a big role, but the attack phase can go on beyond the initial transients and so attack can also involve macrodynamics and/or speed. For example a kick drum is basically just attack-decay, but it's only the initial "tick" which I consider a transient; and with a blown or bowed instrument the attack phase starts with a transient but goes until the timbre has stabilised. In both cases, good transient response is probably not sufficient to portray that convincingly.