Arpeggiators and sequencers have been part of synthesizers since the 1970s, when basic patterns could be played without having to manually press the keys down, allowing complex melodies to be played with 100% accuracy at any speed. Nowadays, sequencers and arpeggiators have become infinitely more complex, mostly due to the fact that they are programmable from a software interface, where a whole song can easily be programmed with a MIDI keyboard and a mouse. The arpeggiator or sequencer built into your trusty synthesizer is not to be ignored however, and the following information will hopefully give you some idea of the power such functions posses.
Arpeggiators are designed to create small melodic patterns from the notes the player gives the synthesizer. For example, the user may hold down the C, E, and G keys on the synthesizer, and with the arpeggiator active it would repeatedly play the selected keys in various different ways depending on how it was programmed. Arpeggiators can play patterns by ascending or descending through the notes like a scale, or by randomly choosing selected notes to play. Modern arpeggiators can do even more, such as perform sub-arpeggiations within the main arpeggio, or use a mask to mute certain notes within the pattern.
Sequencers (sometimes referred to as ‘step sequencers’) are the bigger brother of arpeggiators, allowing full melodic sequences to be programmed. These can be triggered with just a single key press, or in some cases with only a special trigger button. Sequencers for synthesizers come in two hardware forms. The first, being built into the synthesizer itself is not as powerful as its dedicated hardware alternative. The sequencer in a synthesizer will usually only be capable of holding 16 or 32 steps, as well as tempo and shuffle settings. Hardware sequencers are a dedicated hardware unit which can hold many more steps per pattern, as well as chaining patterns together to form a complete song. They are frequently also able to perform modulations to not just the pitch, but also the articulation of the sound – or indeed any aspect of the synthesizer’s architecture. They are an extremely powerful tool when used to their full capabilities, as well as fun to play with. It is not uncommon to see entire songs played with multiple sequencers connected to synthesizers, performing complex actions such as sending MIDI or CV/Gate triggers signals to all devices.