We meet bass virtuoso Jeroen Thesseling, for whom six strings is just not enough. Pic: Jurgen Heerkens Photography

“As far as I know, I have the first seven-string fretless bass that the Warwick custom shop made,” says Jeroen Thesseling, the Dutch bass maestro, and who are we to disagree? This fearsome-looking but beautiful instrument anchors Thesseling’s sublime playing in various bands and sessions, including a tenure with the experimental metal act Obscura. While most players of the metal persuasion do their jobs with the aid of a BC Rich, ESP or Jackson bass, Thesseling is a Warwick devotee for very good reason.

“I’ve been playing 6-string Warwick Thumb basses for 16 years,” he tells us, “and when I started playing with Obscura I found a good balance between the arrangements for the guitars and the bass and the sound of my instrument. What I liked about Thumbs from the beginning was that the instruments have great articulation. There were experimental players like Jack Bruce already using them, of course, and in this kind of metal it’s very hard to make the bass penetrate the music because there is a wall of guitar sound. I always wanted to have a very natural tone that was balanced, plus the string spacing of the neck of the Thumb is really narrow and it’s not a huge neck. I always liked that, and I never had any problems with controlling it.”

Unusually for a player who is primarily active in the metal field, Thesseling’s early influences were decidedly non-riffy in nature. “I started playing fretted Thumbs in late 1993,” he recalls, “when I played in a flamenco ensemble. I played a lot of melodies and chords in that band, and the Thumbs sounded so good that I gave their fretless basses a try – and they were perfect for me, so I decided to concentrate on fretless and put all my fretted basses in a wardrobe. My progress was really fast on the fretless, and now 99% of what I do is fretless. One of my biggest influences is Carles Benavent, who used to play with Paco de Lucia, and he’s a jazz musician. I was inspired by him and his tone, but definitely not his technique, because he plays with a pick and I’ve always preferred to use my fingers.”

Thesseling also plays with the veteran metal act Pestilence, a band which challenges him on many levels, not least in terms of sonic frequency. “Last year I recorded three albums, one with Obscura with a six-string bass, another as a session bassist for a Dutch band and then the last one with Pestilence, which was a nice experience but also pretty difficult, because I went to the studio with a six-string bass and they had a concept in mind about how to play the arrangements. The first idea they had was to have the bass arrangement actually higher than the guitars! Both guitarists in Pestilence use eight-string guitars, so we tried it out. It could have been done that way, for sure, but when I finally reached the studios they’d been there for a week and everything was done apart from the bass. They had been struggling with a six-string bass tuned down, but it just didn’t work: somehow it sounded very strange like that. They were tuned to F# and I was tuned to B, and that was where we struggled, so I used the lowest six strings of a seven-string bass.”

“I started studying melodies in 1995, just to find out what was happening outside the 12-tone equal temperament, so I studied several systems and in the end I came to a system where you can play several scales. In fact it was an 80-tone equal temperament octave, which was extremely dissonant. Every scale had its own color. I set up one of my six-string basses with six strings of the same gauge, but they’re tuned one twelfth-tone apart from each other. That means that the smallest intervals are created by switching strings, and the largest intervals are made by moving to a different point on the same string – in other words, the opposite of the playing technique that we’re used to. I learned a lot from that, and I also trained my ear by using this system. For example, you can play a pure fifth, instead of the fifth that we usually use.”

Once the album was recorded, Thesseling’s challenge was to find a bass that provided both the range and the feel that he was looking for as a touring instrument. “I spoke with Warwick and they said that they would build me a seven-string,” he explains. “I’m an exclusive endorser with them and we’ve been co-operating for years, so they really wanted to help me do this. Of course, it wouldn’t work for Warwick to issue this bass as a signature model because it would be way too expensive for the end user, but it’s an incredible bass. The output goes to a stereo effect and that goes directly to a preamp. I suppose it’s fake stereo, if you like. I don’t use any effects, and it’s interesting that you mention that, because a distorted sound would be easier in the mix. I never use overdrive, though, because I always want that clear tone that will penetrate the guitar sound.”

Take a look at Thesseling’s 7-string and you’d be forgiven for wondering how much this beast weighs, and what the effect of playing it will have on his back. “It’s heavy,” he agrees, “but not much heavier than the regular six-string. My six-strings weigh 5.5 kilos, and the new one is 5.9 kilos. In fact, the body is smaller than the regular six-string neck-through version. As for my back, it’s messed up anyway, because the combination of headbanging and holding the bass in a certain way is terrible: I got a pinched nerve once and the record label hired two women to bounce on my back so I could play again! With instruments like this you really need to have 100 percent control over them: it takes a lot of energy to make sure you hit every note, because you’re on stage with this huge thing, and you have to concentrate even more if you’re headbanging.”

Do you really need all seven strings? “I love this question. Before I got the new 7-string bass I already knew that I was going to use it in a certain way. I knew I was going to focus most on the B, E, A, D and G strings, like a normal 5-string bass, and that I would regard the low F# string in the same way as the high C string. Those two strings are an addition to the normal range of a 5-string bass guitar, as I see it. I’m definitely not going to focus only on the low F#, because that string is just a nice thing that you can add to the arrangements. I think the main reason for me to play this bass is to add something to the arrangements such as a counterpoint. One thing you can do, for example, is play the guitar riff in the opposite mode, so where they go higher you can go lower, which fits perfectly. People write on the internet, ‘It’s a nice bass but you can’t hear the low F#’ – but it’s definitely audible: you’re just not supposed to play all your stuff that low!”