Peter Infeld Double Bass Strings – What do they sound like?

Thomastik’s Peter Infeld double bass strings: A Year in the Trenches

A year is roughly the maximum I want any strings living on my bass, so when I finally took them off, I knew it was time to share everything I’d learned. What follows is my most thorough string evaluation yet: initial impressions, how they settled over months of real-world use, and a direct comparison to my longtime go-to, D’Addario Kaplans.

Several San Francisco Symphony bassists have been trying them, too — they’ve been calling them the “new Bel Cantos. They’ve been on my bass through chamber orchestra concerts, rehearsals, and a whole lot of hours under the bow.

What I Was Coming From

Before the Thomastiks, I had D’Addario Kaplan strings that I’ve been using on and off for about ten years. Before those, I used Pirastro Flexicore Deluxe for years. The Kaplans are similar to the Flexicore Deluxe, maybe just a hair darker, which actually balances well on my bass. It’s a big, full instrument — not overly dark — so a slightly darker string complements it nicely.

My bass is primarily an arco instrument, though the Kaplans work decently for pizzicato. Their response is quick, they grab under the bow fast, and the harmonic overtones are pleasant without being too bright or too dark under my ear. They’re just what I’m used to. They’re also remarkably stable when you first put them on — I can string them up and walk into rehearsal the same day with stable pitch.

First Impressions

The first thing you notice about the Peter Infelds is that they’re noticeably thicker than the Kaplans’ — substantially so. Getting the E string through my tailpiece required some coaxing, and it was so thick that when I was using my extension, turning the peg barely moved it before it would suddenly jump a whole step. Tuning up was genuinely awkward.

Settling was moderate. They needed to come up to pitch three or four times, which is nothing dramatic — nowhere near the wild stretching of Zyex, which can drop a perfect fifth before they stabilize. But they definitely needed a break-in period before I could evaluate them fairly.

There’s a gut-like quality to these strings that I wasn’t expecting. A kind of analog, vintage warmth that’s unusual for steel strings.

In that first session, the A string was noticeably bright. Almost alarmingly so! But within less than an hour of playing, it started to mellow considerably. The E string felt well-balanced right away. And throughout, there was something compelling about how these strings rang: a sustain and bloom that I found immediately appealing, especially when I was working through some solo repertoire.

The sound reminded me of Evah Pirazzi — a Pirastro string that’s very popular in the San Francisco Symphony world. That gut-adjacent character, that organic depth. And physically, these look like Bel Cantos in their wrapping, though the Bel Cantos aren’t quite as thick.

Purchase the Peter Infeld strings from our friends at Gollihur Music

A Year Later: Full Assessment

If you put Spirocores on one end of the spectrum (jazz, growl, the classic street-corner sound) and Bel Cantos on the other (bowed, buttery, orchestral warmth), these prototypes land somewhere meaningfully in the middle. They’re not Spirocore. They’re definitely not Bel Canto. But they borrow something from each.

I’ll say this clearly: I prefer these prototypes to Bel Cantos on my bass, by a significant margin. Bel Cantos have always felt slightly tubby on my instrument — the response is a bit slow, a bit too round. The

Peter Infelds are much quicker to speak, and their tone is more complex. That gut-like quality I noticed on day one never entirely went away. By a couple of weeks in, they’d hit their stride and maintained it.

What I Loved

The arco sound is genuinely beautiful. Even across all four strings, rich with harmonic complexity, and with a kind of “blossom” in the tone that I found myself appreciating more and more over time. The pizzicato sound is also surprisingly interesting. It doesn’t have the growl of Spirocore, but there’s a warmth and character there that’s its own thing.

Tuning stability was impressive. Once these had settled in, they were remarkably stable. I could practically tune them and walk onstage.

What Gave Me Pause

The looseness that makes them feel free and resonant also has a downside: the attack. I had to be more deliberate in getting the string to speak cleanly and to grab the fundamental rather than skimming the surface. During a chamber orchestra concert, I noticed that I was getting close to the fingerboard with the E string and actually had to be careful not to buzz. On a stiffer string, that’s rarely a concern. With these, I had to stay more mindful of bow placement and pressure, especially near the bridge.

And then there’s the wolf. My bass has a characteristic wolfy A-flat — manageable, but present. With the Thomastik prototypes, that wolf was significantly more pronounced than with the Kaplans. The pulsations were clearly audible, a rhythmic “wah-wah-wah” that required real compensating technique in orchestral passages. I spent a lot of time fingering an octave to work around it. The Kaplans bring it down to something I can mostly ignore.

Side-by-Side Summary on my Jackstadt double bass

Coming Back to the Kaplans

After a year on the prototypes, putting the Kaplans back on was a revelatory experience — in both directions. They felt almost like solo strings by comparison; that’s how much thinner they are. The E string felt positively delicate. Tuning the extension was suddenly easy again.

And that front-end response, the pop and release I’d been missing? It was right there, immediately, without any extra thought.

What I gave up coming back: that gut-like complexity, that analog warmth, the bloom I’d been loving in the prototypes. The Kaplans are steel strings in the most direct sense — clear, articulate, responsive. Not worse. Different. And for my orchestral work, that directness is genuinely useful.

Every bass is different. Every player is different. But the Peter Infelds are going to work extremely well for a lot of people — and they’re a significant step forward from the Bel Canto formula.

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