8 ms·
Stack operations on a guitar loop pedal
- InitialLastName 6y agoIsn't the ability to back out of the stack context basically half the point of stack operations? Without the LIFO behavior, it's not really a "stack" in any computational sense.
- whatrocks 6y agoYou definitely can pop off the last layer in the loop stack, but my particular pedal seems to require another accessory in order to be able to do that (there's a separate pedal you attach to this one).
- chrisweekly 6y agoI've enjoyed my Boss RC-50 (a nice upgrade to the RC-20 I had prior) as a live-looping guitar + vocals pedal for years. It makes it easy to create and layer loops, even when only using the built-in foot controls. Highly recommended.
- chrissnell 6y agoI loved the song video in this post and it’s inspired me to try a little of this. Is there a good software solution for this? (Bonus points for Linux support)
- Raro 6y agoI like the suggestion of the analogy in general. But a metaphor I'd use is a feedback system with a very long delay and very low decay constant. So definitely cyclic from that perspective! The signal chain is often split by guitarists with a dedicated A/B box too. So a fuller analogy would be a more complex pipeline.
- whatrocks 6y agoYeah, my analogy is definitely hampered by my novice-level guitar chops. I'm definitely intrigued by the idea of better understanding these complex signal pipelines. In fact, a usesthis.com style website that shows the pedal box arrangements and signal flow diagrams for various guitarists would be a website I'd quite enjoy visiting.
- InitialLastName 6y agoNot guitar-oriented, but modulargrid.net has some big people on it (often obscured for security purposes). You can occasionally see guitarists' signal flows and stopbox arrays in interviews etc, but the truth is usually obscured by prestige, sponsorship concerns, and the logistics of touring.
- Raro 6y agoThank you for this. I am currently bread-boarding two guitar pedals for myself, and there is great discussion on modulargrid.net on filtering. > You can occasionally see guitarists' signal flows and stopbox arrays in interviews etc It's amazing how much influence these interviews have. They have, in the past, directly led to surges in demand for, e.g. the Klon Centaur and variacs.
- InitialLastName 6y agoTrust me, people in the pedal-making industry know exactly how much influence those interviews have, and that's why they put so much effort into making those artists happy.
- bonzini 6y agoThey don't make them "as happy" as you might imagine. Even a guitarist that is good enough to do European tours and get an endorsement deal will get discounts of 20% (on pretty expensive stuff for which they would have to fork out 2000 euros), maybe 30% on bespoke instruments that cost even more.
- UncleEntity 6y agoDuring one of my daily perusals of the YouTubes I came across KT Tunstall[0] going into detail on how she does live looping for her shows. Apparently, I'm not up on the pop scene, she's pretty well respected as one of the best 'loopers'. [0] https://www.youtube.com/watch?v=liOOHp61nZE https://www.youtube.com/watch?v=liOOHp61nZE
- PaulDavisThe1st 6y agoI don't want to be dismissive of any musician's practices and work, but I couldn't really see much evidence in that video or a quick YT search for KT Tunstall as a really good looper. If you want to get an idea of how far you can go with live looping, this is one of my favorite videos (Rico Loop wandering around Berlin with looper, a mic and not a whole lot more). https://www.youtube.com/watch?v=CWc3W8WgFWw https://www.youtube.com/watch?v=CWc3W8WgFWw
- resu_nimda 6y agoMark Rebillet is pretty good. https://www.youtube.com/watch?v=sRpUr5iQPIY https://www.youtube.com/watch?v=sRpUr5iQPIY
- lflux 6y agoHer track "Black Horse & The Cherry Tree" live showcases it a lot better - https://www.youtube.com/watch?v=vp0Pt-VFe_g https://www.youtube.com/watch?v=vp0Pt-VFe_g
- gokhan 6y agoThis is what I like https://m.youtube.com/watch?v=Qwb6wPStEpY https://m.youtube.com/watch?v=Qwb6wPStEpY
- PaulDavisThe1st 6y agoNice decision to use a much longer basic loop (12 bars?) which avoids the "this is obviously a live looper" syndrome. Thanks for the link.
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- tenebrisalietum 6y agoThe article doesn't describe a stack. The closest thing is progressive bitwise OR operations on a ring buffer, good until your whole ring buffer is filled with 1s.
- whatrocks 6y agoThis does seem like a better analogy. The visual display on this particular loop pedal is a ring, as well. I'm going to think more about this! [edited: added word "pedal"]
- robotresearcher 6y agoAssuming a typical audio encoding, each time around the loop the new sample value is added (arithmetic add) to the previous value, not bitwise OR. The mean value of a sample is zero, so you can do this forever. (Idealized. In practice you actively normalize to avoid overflow/clipping).
- ericwood 6y agoI guess it's a stack in the sense that each additional loop is being pushed onto a stack of sorts. This is how the Ditto looper I use works, and you can even perform the "pop" operation and back out of an additional layer. I'm working on a digital delay pedal at the moment, and the underlying data structure is really similar in principle to a looper in that it's a ring buffer that continually loops around (although a bit more complex since the delay time can change!) In actual production loop pedals I'm sure there's optimizations that can be done, but a naive implementation of the layering would just mean creating additional buffers for each layer, and keeping the read/write pointers sync'd between all of them. The output then just becomes a mixed version of all of the loops. When a phrase extends beyond the loop length and repeats over itself, the buffer for that given layer would read the existing value and write a mixed version of the two signals.
- jmiskovic 6y agoI worked on this for a while [1], it was quite satisfying to combine electronics, SW and music in single hobby project. My looper had sort of git model with staging area and committed area. Both staging and committed loops were mixed down to output. You could re-record over staging area as many times as you wanted until you were satisfied, then you could mix it down to commited loop. It's like stack but only top-most loop is changeable. That model provided infinite loop overdubs, ability to undo mistake, and used only x2 memory. Regarding your delay effect, I was quite fascinated by how analog delay pedals allowed live-changing of loop length and the resulting effect it would produce [2]. I researched into the bucket brigade IC, quite interesting stuff. I think in digital you'd have all kinds of nasty glitches if you tried to do it with simple pointer modifications. [1] https://github.com/jmiskovic/DSPedal/ https://github.com/jmiskovic/DSPedal/ [2] https://www.youtube.com/watch?v=xJPde-C28iU https://www.youtube.com/watch?v=xJPde-C28iU
- ericwood 6y agoI love the idea of a "staging area"! That's a very smart and maps 1:1 with the behavior on most loopers I've used. Anything else would require nearly unbounded memory, and memory is easily the most expensive component of any looper. The repitching effect happens because the output from the ring buffer is effectively being resampled. Implementing this is a little funky, but with some clever tricks in how the ring buffer is used and some form of interpolation, you can get essentially the same effect. Here's my implementation, which uses Hermite interpolation: https://github.com/eric-wood/delay/blob/main/src/delay.rs https://github.com/eric-wood/delay/blob/main/src/delay.rs
- raleighm 6y agoWhat I love about loop pedals is it makes time a musical instrument. Brian Eno played with this. Dustin Wong is a delight. Dustin Wong https://www.youtube.com/watch?v=j1PuWrE9nKY https://www.youtube.com/watch?v=j1PuWrE9nKY