String tuning

[bassist_lewis]

When I'm bowing I've noticed that sometimes the note will change pitch slightly (semitone or a bit less) and back again. Before you ask, it's not my left hand shifting.

I've also found that the strings constantly go out of tune after a day or two, could these be related?

Thanks

[Beer of the Bass]

What strings are you using? I've noticed this happening with the solid-core strings that often come on new basses, but less so with quality stranded steel core or synthetic core strings.

[bassist_lewis]

I don't know the brand but they're the ones that came with the bass from thomann

[Beer of the Bass]

I don't know what the Thomann basses come with, but I've played a couple of new Chinese basses which came with really cheap strings. Because they're made with a plain wire core (like bass guitar strings) rather than a flexible braid, the stiffness causes them to go sharp when bowing loudly or with firm pressure. Loud pizz notes come out slightly sharp at the attack, then return to pitch as the note decays. It tends to be more pronounced on the lower strings. Does that sound like what you're hearing?
If you've got a set of those strings, almost any quality string will be a big improvement.

[Marty Forrer]

Unless your bass was set up properly before purchase, it is likely that it came with "shipping" strings, which are typically only suitable for building a fence. This is a standard procedure for Chinese basses, and most any stringed instrument.

[SubsonicSimpleton]

It is possible to recreate this pitch change at will on my bass (which is strung with spirocores) - if you start bowing a note over the end of the fingerboard using some vigour and plenty of weight, and then slide the bow down the string towards the bridge (while continuing to draw it across the string) the note will change pitch and return to its original pitch. On my bass it's really easy to do this on the E and A and gets progressively more difficult to cause on the D and G strings - I discovered this by accident the other day when sitting down to practise when I was really physically tired, and I was slumping forward involuntarily while playing, noticed this pitchchange happen once and figured out how to recreate it.

I'm not really sure exactly what causes or enables the pitch change - I suspect that it has something to do with the bow crossing between the vibration nodes and antinodes on the string, and when the bow is precisely in the antinode where the string has least amplitude it allows the weight you are putting into the bow to depress the string slightly bending the pitch up, but when the bow is on a positive node the energy in the string resists the pressure being applied by the bow hair.

[zbd1960]

All bowed stirng instruments do this: as you apply the pressure to the string and until it 'settles' to normal vibration it usually is sharp for a moment. You can reduce it by not putting too much energy into the string. If you have the bow at the heel and rest it on a stirng, you should find that you can in fact pull the string a fair distance before it overcomes the resistance of the rosin on the hair.

Strings are sensitive to temperature - how much so depends on how they are made and to some extend on the quality of the set-up of the instrument. You need the right level of elasticity and tension for your strings for the set-up of the instrument (e.g. neck/finger board angle, bridge height). My cello experience is that some stirngs are extremely stable. The Jargar stirngs on my previous cello were extremely stable. The stirngs on my German cello (Larson and Spirocore) are not as stable. This is because they are more elastic and are more sensitive to temperature change. Taking the cello out of a cold car, they tnd to be sharp because they've shrunk slightly. In warm weather, they go flat as the strings lengthen.

Although bass strings are much heavier, they will still exhibit this behaviour to some extent.

Edited April 6, 2016 by zbd1960

[Beer of the Bass]

[quote name='zbd1960' timestamp='1459985813' post='3021605']
All bowed stirng instruments do this: as you apply the pressure to the string and until it 'settles' to normal vibration it usually is sharp for a moment. You can reduce it by not putting too much energy into the string. If you have the bow at the heel and rest it on a stirng, you should find that you can in fact pull the string a fair distance before it overcomes the resistance of the rosin on the hair.
[/quote]

Agreed, it will always happen to some extent, but I mention the string type as I've found that is more pronounced on the plain steel core strings you get on a lot of new basses. I'm not fully up to speed on the physics of this, but I presume that the stiffness of the core is a factor.
When I was first changing over from EUB to double bass I rented a cheap plywood bass for a few months which had the original strings, and changing them out for a set of Thomastik Superflexibles was a huge improvement in intonation and pitch stability. The tone and volume from the instrument were improved too.