[Julien] is one of those cool dads who shows his love with time invested rather than money spent. His daughter plays the harp, and you would not believe the price of concert harps. Even the cheap ones are several thousand USD. So naturally, he decided he would build her a MIDI concert harp from the ground up.
This plucky work in progress uses a strain gauge and an AD620 amplifier on every string to detect the tension when plucked. These amplifiers are connected to Arduinos, with an Arduino every nine strings. The Arduinos send MIDI events via USB to a Raspberry Pi, which is running the open synth platform Zynthian along with Pianoteq.
The harp is strung with guitar strings painted with silver, because he wanted capacitive touch support as well. But he scrapped that plan due to speed and reliability issues. Strain past the break to check out a brief demo video.
[Julien] used strings because he wanted to anchor the harpist in tactility. But you’re right; many if not most MIDI harps use lasers.
impressive! Cool project!
Really nicely done!
I see she tries to mute the harp at the end. Maybe if the Arduinos sensed slight tension on an octave worth of notes, a MIDI mute like command could be sent to the synthesizer.
An octave is too much. Players want to mute individual strings:
https://www.youtube.com/watch?v=i4dypyJ9BuU
(I know, not her best vocal performance, but the video shows the fingers and strings from different angles.)
Won’t the untuned strings confuse the player? Or is their volume too low to be heard while the synthesizer is playing?
I think they are inaudible unless that little speaker can is the source the sound of the synth engine. They would be like bass tone, as that shape is no musical scale to begin with.
What a wonderful rabbit hole I have fallen into. Zynthian! In an answer to my questions, a raspberry Pi can run ZynAddSubFX inside of this package of apps and run accessory audio out at 24/96 all in a neat box suitable for live portable playing. Open source! I have used ZynAddSubFX for years, now I wouldn’t need a USB MIDI cable and a laptop or two.
“Strain past the break”
I see what you did there.
B^)
Thanks for your comments !
In fact, she can mute the strings (when the tension rises) but I also have to debounce each string. So, sometimes, you can’t mute string untill the debounce ends. I’ll have to improve it in the future
Bad tune on the video, because the harp is one octave too low. It’s fixed now. I’ll post a new video in a couple of weeks, using other song than harp because my daughter really enjoy it.
I’ve tried to mute strings as much as possible (poorman’s way, using rubber tape for windows), so the string volume is very low. I’m thinking to add a feedback close to her ears, so she won’t be able to listen to the real string at all.
I’ve been reading this blog for years now, I’m proud to be a part of it now ;-)
Julien
what harp sample is this midi harp triggering? For instance, in a music production software like Logic, one could load any number of harp sample sets from Cinesamples, Berlin Symphonic, Simple Sam etc.
I use the pianoteq “concert harp” ones. The pianoteq demo is included in the zynthian image. Those sample are quite accurate, compared to a real harp.