There are loops available:

https://www.youtube.com/results?search_query=harp%20glissando%20sound%20effect&sm=1

However:

A harp gliss is one of the easiest things to create using a MIDI keyboard and a fair to good Harp, Nylon String Guitar, or some other suitable Patch sound.

Anybody with two working hands can play this one - even if the only other thing they can play might be chopsticks.

It is an easy effect.

The "Classic" harp gliss is done by using only the black keys on the keyboard, inverting the hands upside-down and raking the two hands up or down the black keys, one behind the other, while holding the Sustain Pedal down. Once created, this can be Transposed to any of the 12 keys as necessary to fit the target piece easily, using MIDI commands, either as a key transposition, or in some cases, by using the PianoRoll view in your DAW to select all notes and drag them to a different key all at once.

Raking the black keys yields and automatic Pentatonic Scale harp gliss and is the most common one for this effect. Raking the white keys is used less often, for that creates a Diatonic (Major) scale sound and the held Sustain Pedal makes it sound like too many enharmonic notes at once. But as with all things, there are times and places for it, for example, the typical "dream" sequence sound that might be needed for an underscore or other dramatic musical effect can contain BOTH the black key rake along with some White Key rakes, which can serve to extend the amount of time the repeated effect takes place without things becoming too trite sounding or repetitive.

I have found through using many different types of MIDI synths and samples that it is often the case where any Patch that is labeled as "harp" doesn't sound as good or as realistic at the Gliss thing as some of the OTHER patches in the synth or soundbank, which may be labeled as just about any instrument OTHER than harp, but work to to the better once the Gliss is recorded as MIDI and Reverb is added to it, so experiment with changing patches and listening within the context of the particular project. Sometimes "Dulcimer" patches can sound good, or Nylon Guitar, etc. Depends on lots of issues, changes from synth to synth, sample to sample.

The Black Key/White Key Keyboard Rake is EASY, takes a minimum of "practice" at it to sound like a pro.


--Mac