For example, on a musical instrument synthesiser use brass' and 'organ' rather than 'brass1' and 'brass2'. However, instruments that sound different in real life may not when played on a synthesiser, so care should be taken when choosing timbres. Using multiple timbres per earcon may confer advantages when using compound earcons. Using the same timbres for similar things and different timbres for other things helps with differentiation of sounds when playing in parallel. There is also another reason why care must be taken when timbres are chosen.
Some timbres are continuous and some are discrete.
They only last a short time. This is the nature of different musical instruments. If continuous sounds are needed to sonify an interaction then discrete sounds would have to be constantly turned on and off if they were to be used. This can limit the choice of available timbres. A combination of register and another parameter would give better performance.