More Info on Glockenspiel Overtones
It is possible to produce rather consistent overtones on [at least] a [Mapex-brand] glockenspiel, which is an interval of 1 octave and a perfect 4th above the given fundamental. i.e. E7 → A8. (This is done by stopping the bar at the center point between the nodes and then bowing the bar.) However, there are additional possibilities which are listed below, all of which are unconventional and not feasible for actual use in performance / composition.
These observations have been made while trying to find as many different sounds as possible for Connor's larger Extreme Notes project. Composing with the intention of producing overtones in any way beyond the initial method is not practical, however, these pitches are still produced by some musical means and are very high [in frequency], thus they are documented here out of interest and curiosity.
Below is a list of all of the intervals observed in overtone experimentation. Following that is a description of the method of achieving these sounds, as well as additional notes for those findings. The methods of overtone production described below include:
[1] Bowing Underneath the Bar at a Diagonal Angle
[2] Pressing on Node, then Bowing (Olds Glockenspiel)
[3] Pressing on Node, then Striking Edge of Bar at Other Node
[4] Side of Bar at the Node, with a Mini Wrench
[5] Findings on Modified Lower Bars
Last Updated: August 24, 2024
These observations have been made while trying to find as many different sounds as possible for Connor's larger Extreme Notes project. Composing with the intention of producing overtones in any way beyond the initial method is not practical, however, these pitches are still produced by some musical means and are very high [in frequency], thus they are documented here out of interest and curiosity.
Below is a list of all of the intervals observed in overtone experimentation. Following that is a description of the method of achieving these sounds, as well as additional notes for those findings. The methods of overtone production described below include:
[1] Bowing Underneath the Bar at a Diagonal Angle
[2] Pressing on Node, then Bowing (Olds Glockenspiel)
[3] Pressing on Node, then Striking Edge of Bar at Other Node
[4] Side of Bar at the Node, with a Mini Wrench
[5] Findings on Modified Lower Bars
Last Updated: August 24, 2024
Possible Intervals
The following intervals have been encountered as overtones above glockenspiel bars' fundamentals.
• Variable
[1] Bowing the node underneath the bar at a diagonal angle produces a pitch that ranges from approximately 2 octaves to a major 6th which creates a resultant "chromatic scale" of overtones of just over an octave across a 2.5-octave instrument; on a Mapex-brand glockenspiel, an F5 key produced F7 whereas C8 produced A8.
[2] Striking the side of detuned G5–B5 bars (sounding C5–E5) at its nodal point with a thin metal beater produced a consistent overtone 2 octaves and a major 6th higher, but an F8 also rung out from each of these keys except for C#5, which produced a C#8 instead (3 octaves). The F8's distance is 3 octaves and a perfect 4th from C5 whereas it is 3 octaves and a major 2nd from E5. This would appear to be the first transverse mode of the plane of the bar (Fletcher & Rossing) in relation to the original bars; i.e. a distance of about just under 3 octaves from an original G5–B5. However... (see note 3):
[3] Stopping the bar at nodal point and then striking the bar [with a mallet] at the other node, very close to the side of the bar, produced a similar phenomenon. F5 and F#5 produced a pitch 3 octaves higher, but this gradually contracted to 2 octaves and a perfect 4th by the A6 key, above which the lower overtone (at the octave and perfect 4th relationship) dominated the sound. This interval appeared to "contract" similarly to bowing underneath the bars at a diagonal angle.
• Octave + Perfect 4th:
[1] Stopping bar at center point between nodes, then bowing; on Mapex-brand glockenspiel, upper limit of E7 key (i.e. A8).
// [main method for intentional compositional use]
[2] Striking side of bar at nodal point with thin metal beater, above C7 key; upper limit of ~B7 key (i.e. E9).
(this also was able to produce an overtone 2 octaves and a major 2nd higher)
• Note: this interval is very close to the 2nd transverse mode of vibration for uniform free bars (2.71 / Fletcher & Rossing; 2.756 / Hopkin)
• 2 Octaves + Major 2nd:
Striking side of bar at nodal point with thin metal beater, above C7 key; upper limit of ~Ab7 key (i.e. Bb9).
(this also was able to produce an overtone 1 octave and a perfect 4th higher)
• 2 Octaves + Minor 3rd:
Bowing the node underneath the bar at a diagonal angle; specifically observed on C#7 key (i.e. E9) on Mapex-brand glockenspiel, this was inconsistent with this method's more variable results, described above.
• 2 Octaves + Major 3rd:
Striking side of bar at nodal point with thin metal beater; upper limit of ~Ab6 key (i.e. C9).
• Note: this interval is close to the 3rd transverse mode of vibration for uniform free bars (5.15 / Fletcher & Rossing; 5.404 / Hopkin)
• 2 Octaves + Perfect 5th:
Bowing the node underneath the bar at a diagonal angle; specifically observed on Eb6 key (i.e. Bb8) on Mapex-brand glockenspiel, this was inconsistent with this method's more variable results, described above.
• 2 Octaves + Minor 6th:
Stopping bar at nodal point, then bowing; produced on Olds-brand glockenspiels, upper limit of D#6 key (i.e. B8).
• 2 Octaves + Major 6th:
Striking side of bar at nodal point with thin metal beater; specifically observed on C5–E5 keys (i.e. A7–C#8) whose backside was drilled down from bars originally tuned G5–B5. (The detuning of the bars may be relevant to this phenomenon.)
The following intervals have been encountered as overtones above glockenspiel bars' fundamentals.
• Variable
[1] Bowing the node underneath the bar at a diagonal angle produces a pitch that ranges from approximately 2 octaves to a major 6th which creates a resultant "chromatic scale" of overtones of just over an octave across a 2.5-octave instrument; on a Mapex-brand glockenspiel, an F5 key produced F7 whereas C8 produced A8.
[2] Striking the side of detuned G5–B5 bars (sounding C5–E5) at its nodal point with a thin metal beater produced a consistent overtone 2 octaves and a major 6th higher, but an F8 also rung out from each of these keys except for C#5, which produced a C#8 instead (3 octaves). The F8's distance is 3 octaves and a perfect 4th from C5 whereas it is 3 octaves and a major 2nd from E5. This would appear to be the first transverse mode of the plane of the bar (Fletcher & Rossing) in relation to the original bars; i.e. a distance of about just under 3 octaves from an original G5–B5. However... (see note 3):
[3] Stopping the bar at nodal point and then striking the bar [with a mallet] at the other node, very close to the side of the bar, produced a similar phenomenon. F5 and F#5 produced a pitch 3 octaves higher, but this gradually contracted to 2 octaves and a perfect 4th by the A6 key, above which the lower overtone (at the octave and perfect 4th relationship) dominated the sound. This interval appeared to "contract" similarly to bowing underneath the bars at a diagonal angle.
• Octave + Perfect 4th:
[1] Stopping bar at center point between nodes, then bowing; on Mapex-brand glockenspiel, upper limit of E7 key (i.e. A8).
// [main method for intentional compositional use]
[2] Striking side of bar at nodal point with thin metal beater, above C7 key; upper limit of ~B7 key (i.e. E9).
(this also was able to produce an overtone 2 octaves and a major 2nd higher)
• Note: this interval is very close to the 2nd transverse mode of vibration for uniform free bars (2.71 / Fletcher & Rossing; 2.756 / Hopkin)
• 2 Octaves + Major 2nd:
Striking side of bar at nodal point with thin metal beater, above C7 key; upper limit of ~Ab7 key (i.e. Bb9).
(this also was able to produce an overtone 1 octave and a perfect 4th higher)
• 2 Octaves + Minor 3rd:
Bowing the node underneath the bar at a diagonal angle; specifically observed on C#7 key (i.e. E9) on Mapex-brand glockenspiel, this was inconsistent with this method's more variable results, described above.
• 2 Octaves + Major 3rd:
Striking side of bar at nodal point with thin metal beater; upper limit of ~Ab6 key (i.e. C9).
• Note: this interval is close to the 3rd transverse mode of vibration for uniform free bars (5.15 / Fletcher & Rossing; 5.404 / Hopkin)
• 2 Octaves + Perfect 5th:
Bowing the node underneath the bar at a diagonal angle; specifically observed on Eb6 key (i.e. Bb8) on Mapex-brand glockenspiel, this was inconsistent with this method's more variable results, described above.
• 2 Octaves + Minor 6th:
Stopping bar at nodal point, then bowing; produced on Olds-brand glockenspiels, upper limit of D#6 key (i.e. B8).
• 2 Octaves + Major 6th:
Striking side of bar at nodal point with thin metal beater; specifically observed on C5–E5 keys (i.e. A7–C#8) whose backside was drilled down from bars originally tuned G5–B5. (The detuning of the bars may be relevant to this phenomenon.)
[1] Bowing Underneath the Bar at a Diagonal Angle
Between 2018 and 2020, Connor experimented with trying to produce overtones on a glockenspiel. He originally experimented with an Olds-brand instrument and found that a pitch could be produced by bowing underneath the bar at an angle. The resulting pitch range across the 2.5-octave instrument was a quasi-chromatic scale from G7–A8.
Separately, on a Mapex-brand instrument, a similar "underneath-bar" scale from F7–A8 was possible. Some keys had very similar pitches, likely tied to the dimensions of the bar without accounting for tuning modifications on the underside of the bar, which change the overall pitch. The inherent interval here is inconsistent; C8 producing an A8, a major 6th higher, is a smaller distance than F5 producing an F7 at a distance of 2 octaves.
In a separate session in 2024, this method also produced a Bb8 from the Eb6 key. This is an octave higher than what might have been expected from the "instrument chromatic scale" pattern. The C#7 key produced an E9, which is much higher than what the method is "supposed" to generate, and is a different unique interval from the Eb6 key as well.
[2] Pressing on Node, then Bowing (Olds Glockenspiel)
Another unique overtone appeared present on Connor's Olds-brand glockenspiel. Pressing on one of the nodes, just by where the bar is screwed into the frame, and then bowing the edge of the bar produced an overtone approximately 2 octaves and a minor 6th higher, not speaking higher than the D#6 key, which produced B8.
[3] Pressing on Node, then Striking Edge of Bar at Other Node
Inspired by the multiphonic harmonic discovery on vibraphone by Edgerton and Tzschoppe in 2022, pressing on one node and striking the very edge of the bar close to the other node (or even the center of the bar) allowed a much higher pitch to ring out. It appeared at first that the result was an interval of about 3 octaves, which would be equivalent to the first transverse mode of the plane of the bar (Fletcher & Rossing), but this interval began to grow smaller as higher bars were tested. An F8 appeared above F5, whereas a G8 appeared above A5. The "main" overtone of 1 octave and a perfect 4th slowly became more audible through this method, arguably overtaking the sound of the "super high contracting interval" at F#6 or G6. At F#6, the higher overtone was approximately C9 at 2 octaves and an augmented 4th. Nothing significant was perceptible beyond A6 (showing a D9 peak in a spectral analysis).
Mentioned below, striking the node directly with a small, thin metal wrench on detuned G5–B5 bars (which sound a perfect 5th lower), shows a very similar result. Although in that case, there appeared to be almost a "fixed" F8 ringing out from now-C5, D5, and E5 bars. The interval to F8 from these lower bars does follow a possible pattern here of this interval expanding as the fundamental becomes lower. It is possible that this pattern is dependent on the dimensions of the bar without accounting for tuning modifications on the underside of the bar, which change the overall pitch.
[4] Side of Bar at the Node, with a Mini Wrench
The "beater" may vary, but Connor used a small, thin metal wrench and struck the side of the bars along the thin edge at approximately the nodal points. From Gb5 to Ab6, this produced a pitch that was 2 octaves and a major 3rd higher, i.e. Gb5 produced Bb7 and Ab6 produced C9. Subsequently, the C#7, G#7, and B7 bars only appeared to produce overtones an octave and a perfect 4th higher, as "normal," when struck in this way at the side of the node. Theoretically, these bars would have produced F9, C10, and D#10, the first two of which are within the generally accepted threshold of human hearing, although these frequencies may not have been picked up from the analysis software used, if they were even produced at all.
In a separate session, this same method appeared to produce a pitch 2 octaves and a major 2nd above the fundamental of the bar. There was a very faint high-pitched squeal experienced in person, but this pitch appeared consistent in spectral analysis. The bars tested where this occurred was D7, Eb7, F7, and Ab7, resulting in pitches E9, F9, G9, and Bb9 respectively. The Bb7 and B7 keys both produced a peak at Ab8, suggesting limits of the analysis software, or presence of the pitch at all, and do not appear to be related to the lower bars' pattern. (Other unrelated harmonic peaks appeared as well.) Even if it were practical for performance, it is unclear how to differentiate more specifically how to achieve the octave + perfect 4th overtone VS the 2 octaves + major 2nd overtone with this method. It is also unclear if this major 2nd is actually incorrect and the interval pattern remains consistent from the lower bars.
[5] Findings on Modified Lower Bars
In 2020, Connor had five bars tuned down from their original state while repurposing parts from an Olds-brand glockenspiel in order to produce his Piccolo Glockenspiel. The tuning process consisted of drilling additional holes into the back of the keys, which resulted in lowering the pitch by a perfect 5th for G5–B5 bars. On each of these bars a pitch approximately 2 octaves and a major 6th resonated when striking the node with a small, thin metal wrench. These pitches corresponded to A7 (from C5) up to C#8 (from E5).
In addition to this, for each of these adjusted keys except for the C#5, an additional high pitch appears in a spectral analysis that hovers around F8 with microtonal adjustments in both directions. With additional testing, it was possible for this sound to be perceived very clearly and separately from other pitches that were produced by the C5 and E5 keys. Reproducing this would not be easily possible at all. (The C#5 key appeared to produce a very strong C#8 instead of the F8.) This would equate to an interval of 3 octaves and a perfect 4th from C5 (or 2 octaves and a minor 7th above the original G5) and 3 octaves and a major 2nd from E5 (or 2 octaves and a diminished 5th from B5).
Described above is a potential pattern of a variable overtone which appears to contract in distance from higher fundamentals which appears to align with these higher F8 overtone intervals. Ultimately, it is not clear if these F8s appear due to changed overtone relationships caused by the excessive removal of metal from the underside of the bars or if the lower fundamental allows for higher-pitched overtones to emerge more noticeably.
Between 2018 and 2020, Connor experimented with trying to produce overtones on a glockenspiel. He originally experimented with an Olds-brand instrument and found that a pitch could be produced by bowing underneath the bar at an angle. The resulting pitch range across the 2.5-octave instrument was a quasi-chromatic scale from G7–A8.
Separately, on a Mapex-brand instrument, a similar "underneath-bar" scale from F7–A8 was possible. Some keys had very similar pitches, likely tied to the dimensions of the bar without accounting for tuning modifications on the underside of the bar, which change the overall pitch. The inherent interval here is inconsistent; C8 producing an A8, a major 6th higher, is a smaller distance than F5 producing an F7 at a distance of 2 octaves.
In a separate session in 2024, this method also produced a Bb8 from the Eb6 key. This is an octave higher than what might have been expected from the "instrument chromatic scale" pattern. The C#7 key produced an E9, which is much higher than what the method is "supposed" to generate, and is a different unique interval from the Eb6 key as well.
[2] Pressing on Node, then Bowing (Olds Glockenspiel)
Another unique overtone appeared present on Connor's Olds-brand glockenspiel. Pressing on one of the nodes, just by where the bar is screwed into the frame, and then bowing the edge of the bar produced an overtone approximately 2 octaves and a minor 6th higher, not speaking higher than the D#6 key, which produced B8.
[3] Pressing on Node, then Striking Edge of Bar at Other Node
Inspired by the multiphonic harmonic discovery on vibraphone by Edgerton and Tzschoppe in 2022, pressing on one node and striking the very edge of the bar close to the other node (or even the center of the bar) allowed a much higher pitch to ring out. It appeared at first that the result was an interval of about 3 octaves, which would be equivalent to the first transverse mode of the plane of the bar (Fletcher & Rossing), but this interval began to grow smaller as higher bars were tested. An F8 appeared above F5, whereas a G8 appeared above A5. The "main" overtone of 1 octave and a perfect 4th slowly became more audible through this method, arguably overtaking the sound of the "super high contracting interval" at F#6 or G6. At F#6, the higher overtone was approximately C9 at 2 octaves and an augmented 4th. Nothing significant was perceptible beyond A6 (showing a D9 peak in a spectral analysis).
Mentioned below, striking the node directly with a small, thin metal wrench on detuned G5–B5 bars (which sound a perfect 5th lower), shows a very similar result. Although in that case, there appeared to be almost a "fixed" F8 ringing out from now-C5, D5, and E5 bars. The interval to F8 from these lower bars does follow a possible pattern here of this interval expanding as the fundamental becomes lower. It is possible that this pattern is dependent on the dimensions of the bar without accounting for tuning modifications on the underside of the bar, which change the overall pitch.
[4] Side of Bar at the Node, with a Mini Wrench
The "beater" may vary, but Connor used a small, thin metal wrench and struck the side of the bars along the thin edge at approximately the nodal points. From Gb5 to Ab6, this produced a pitch that was 2 octaves and a major 3rd higher, i.e. Gb5 produced Bb7 and Ab6 produced C9. Subsequently, the C#7, G#7, and B7 bars only appeared to produce overtones an octave and a perfect 4th higher, as "normal," when struck in this way at the side of the node. Theoretically, these bars would have produced F9, C10, and D#10, the first two of which are within the generally accepted threshold of human hearing, although these frequencies may not have been picked up from the analysis software used, if they were even produced at all.
In a separate session, this same method appeared to produce a pitch 2 octaves and a major 2nd above the fundamental of the bar. There was a very faint high-pitched squeal experienced in person, but this pitch appeared consistent in spectral analysis. The bars tested where this occurred was D7, Eb7, F7, and Ab7, resulting in pitches E9, F9, G9, and Bb9 respectively. The Bb7 and B7 keys both produced a peak at Ab8, suggesting limits of the analysis software, or presence of the pitch at all, and do not appear to be related to the lower bars' pattern. (Other unrelated harmonic peaks appeared as well.) Even if it were practical for performance, it is unclear how to differentiate more specifically how to achieve the octave + perfect 4th overtone VS the 2 octaves + major 2nd overtone with this method. It is also unclear if this major 2nd is actually incorrect and the interval pattern remains consistent from the lower bars.
[5] Findings on Modified Lower Bars
In 2020, Connor had five bars tuned down from their original state while repurposing parts from an Olds-brand glockenspiel in order to produce his Piccolo Glockenspiel. The tuning process consisted of drilling additional holes into the back of the keys, which resulted in lowering the pitch by a perfect 5th for G5–B5 bars. On each of these bars a pitch approximately 2 octaves and a major 6th resonated when striking the node with a small, thin metal wrench. These pitches corresponded to A7 (from C5) up to C#8 (from E5).
In addition to this, for each of these adjusted keys except for the C#5, an additional high pitch appears in a spectral analysis that hovers around F8 with microtonal adjustments in both directions. With additional testing, it was possible for this sound to be perceived very clearly and separately from other pitches that were produced by the C5 and E5 keys. Reproducing this would not be easily possible at all. (The C#5 key appeared to produce a very strong C#8 instead of the F8.) This would equate to an interval of 3 octaves and a perfect 4th from C5 (or 2 octaves and a minor 7th above the original G5) and 3 octaves and a major 2nd from E5 (or 2 octaves and a diminished 5th from B5).
Described above is a potential pattern of a variable overtone which appears to contract in distance from higher fundamentals which appears to align with these higher F8 overtone intervals. Ultimately, it is not clear if these F8s appear due to changed overtone relationships caused by the excessive removal of metal from the underside of the bars or if the lower fundamental allows for higher-pitched overtones to emerge more noticeably.