The Quadra arpeggiator have a really nice feature that really enhances the sound of the Quadra. You can use the arpeggiator with the hold footswitch and/or the trill feature. One thing to do with the Quadra is to use it with an ARP 1601 sequencer. Thanks to all those input jacks on the Quadra, it is the ultimate synth to use with a sequencer.
For example: 1) You can use all 16 steps of the ARP sequencer to control the bass synth.
2) With the sequencer still connected to the bass synth, turn on the arpeggiator and you can hear a bass sequence as you play arpeggios on the lead synth and chords on the polysynth and/or string section.
3) You can also use all 16-steps of the sequencer to control the lead synth.
4) For some really wild and complicated sequenced sounds add some trill to Osc 2 and/or turn on the arpeggiator as the sequencer controls the lead synth.
5) Put the sequencer in 8/2 mode and you can send an 8-note sequence to the Quadra's bass synth while sending a totally different 8-note sequence to the Quadra's lead synth.
6) For more complex sounds, do as 5) and add trill and/or use the arpeggiator.
7) With the sequencer in 8/2 mode, send one 8-note sequence to VCO-1 of the lead synth and the other 8-note sequence to VCO-2 of the lead synth. This produces some great duophonic sequences.
8) There are also some rather innovative ways to produce 3-note chordal sequences although it is a bit complex to explain here. Do to the Quadra's unique and innovative design, there are many other unusual things you can do with and without a sequencer. Although the Quadra's polyphonic section had only 1-filter and was not truly polyphonic like its main competitors, the Prophet-5 and Oberheim 4-voice, it was the only 70's era polyphonic/paraphonic synth that was multi-timbral (capable of producing 4 different sounds at once). (I guess the CS-80 was duo-timbral.)