The first model, introduced in 1985, was the Pad-8. It was an influential device at that time, allowing drummers and percussionists the opportunity to trigger virtually any MIDI sound source without the need of a full electronic drum set. It had no internal sound source, and all pads were assignable to one note each. All pads were on the same MIDI channel.
The second model, introduced in 1989, was the Pad-80 Octapad II. Again the Pad-80 was an eight pad MIDI controller that allowed for various types of MIDI sound sources. Improvements in this second model included the ability to play up to three notes per pad, and velocity switching, which allowed the user to stack or alternate between the assigned notes depending on how hard the pads were struck. This feature became useful for creating more realistic sounding drum parts, and in addition allowed drummers to play melodic instruments with greater ease. These new features were groundbreaking at the time, and are still utilized in Roland's electronic percussion today.
The memory was increased, allowing up to 64 different patches internally and another 64 patches to be stored on a Roland M-256E memory card. Further improvements to the MIDI specification included the control of modulation, pitch bend and aftertouch using a foot pedal, along with full System Exclusive (SysEx) capability. The Pad-80 had a patch chain function that allowed a series of 32 patches to be arranged in any sequence, eight of these chains could be stored in memory.
After the Pad-80, Roland continued to release SPD-8 with on-board sounds, as a standalone instrument in 1990, SPD-11 in 1993, which not only had more sounds but also built-in effects processing, and SPD-20 in 1998, which had more on-board sounds. These SPD Series products had not been named "Octapad" on the product panel.