Yamaha D1500 digital delay rack unit.
The Yamaha D1500 is a digital delay system with a time range of 0 to 1023 milliseconds in 1 millisecond increments, with full 20Hz to 18kHz frequency response throughout the delay range. It was the first commercially available digital delay with a MIDI interface and follows the success of the R1000 digital reverb.
Any of the D1500's 16 programmable memory banks can be selected remotely from a MIDI instrument. This allows specific delay effects to be assigned to particular instrument voices. The appropriate delays are then recalled automatically as each voice is selected.
For non-MIDI equipment, programmed delays can be recalled simply by selecting the appropriate bank – either manually or by footswitch.