Instruments: At least a part of the characteristic sound of the Vienna Philharmonic has been attributed to the use of instruments that differ from those used by other major orchestras:

• The orchestra's standard tuning pitch is A⁴=443 Hz; the tuning standard for A⁴ is generally considered at a frequency of 440 Hz.

• The VPO uses the German-system (Öhler system) clarinet. By comparison, the Boehm-system clarinet is favored in non-German speaking countries.

• Likewise, while the Heckel bassoon is now the norm for most orchestras around the world, in the VPO the Heckel bassoon is played almost completely without vibrato.

• The rotary-valve trumpet is used, but unlike most other Germanic orchestras the VPO prefers smaller bore rotary trumpets from makers such as Heckel and Lechner.

• Like its counterparts elsewhere in Austria, Germany and Russia, the VPO favors the F bass and B-flat contrabass rotary-valve tuba, whereas the CC piston-valve tuba is preferred in most American and some British orchestras.

• The trombone has a somewhat smaller bore, but this is also true of the trombone used in many German orchestras.

• The timpani have the Schnellar System in which the kettle pushed up as opposed to the head being pulled down. Hans Schnellar was the timpanist in the early 20th century, and personally made these drums. They also use goat skin heads as opposed to calf skin or plastic heads.

• The double bass retains the traditional theater-placement in a row behind the brass. The VPO uses 4- as well as 5-string double basses, with the bow always being held underhand (German bow).

• The Wiener oboe is, along with the Vienna horn (see below), perhaps the most distinctive member of the VPO instrumentarium. It has a special bore, reed and fingering-system and is very different from the otherwise internationally used Conservatoire (French) oboe.

• The Vienna horn in F uses a Pumpenventil. Unlike the rotary valves used on most other orchestral horns, the Pumpenventil contributes to the liquid legato that is one of the trademarks of the Viennese school. The bore of the Vienna horn is also smaller than more modern horns—actually very close to that of the valveless natural horn. The Vienna horn has remained virtually unchanged since the mid-nineteenth century—as a result it is arguably well-suited to the Classical and Romantic repertoire at the core of the VPO's programming.

On the other hand, at least two instruments or instrument families are like those in other orchestras. According to the Vienna Philharmonic's website, "the flute is largely the same as the conventional Böhm flute, which is widely used all over the world. However, it did not replace the wooden flute in Vienna until the 1920's." Also, the Viennese string sound should not be attributed to unique attributes of the instruments, according to the VPO, which writes on its website, "There can be no doubt that the Viennese string instruments themselves, unlike the winds, are not of prime importance in producing the orchestra's unique sound. With a few exceptions, the quality of the instruments of the string section is not particularly outstanding". To be sure, the instruments are of high quality; the National Bank of Austria currently loans four violins made by Antonio Stradivari to the VPO.

The VPO's instruments and their characteristic tone-colors have been the subject of extensive scientific studies by Gregor Widholm and others at the Institute of Music Acoustics (Wiener Klangstil – Viennese Tone Style) at the University of Music and Performing Arts, Vienna. The Vienna Philharmonic's website generalizes about its wind and brass instruments in terms of overtones: "With the exception of the flute and, to some extent, the bassoon, the typical differences in tone of Viennese wind and brass instruments can be described as follows: They are richer in overtones, i.e., the sound tone is brighter."

Playing Styles: The orchestra in 2004 began offering a summer institute, the International Orchestra Institute Attergau for Wiener Klangstil, to instruct other musicians in the Viennese playing style.

Hurwitz notes that the 1960 Walter interview indicates that the strings's vibrato (as of 1960) was audibly like that of 1897, and also quotes music critic Richard Specht in 1919 writing of "something inimitable in the vibrato and the passionate virtuosity of the violins" of the Vienna Philharmonic.

As for other instruments, using early recordings, the musicologist Robert Philip has documented some changes in how VPO players used vibrato during the mid-20th century, although he also notes differences between the VPO and other orchestras of the era. As was typical of the era, the pre-1945 flutes show "very little vibrato" in recordings "until after World War II... even in the long solo in Mahler's Das Lied von der Erde the flautist [under Bruno Walter in 1936]... plays almost without vibrato" except on "a few long notes [with] a delicate medium-speed vibrato"; but "by the late 1940s the flautists... had adopted a gentle medium-speed vibrato". The oboes before the 1940s show "little or no vibrato," but by the late 1940s "the principal oboist had adopted a very delicate fast vibrato ... but he uses it very sparingly." (The cor anglais is, he notes, even in the late 1940s still played "without any vibrato"). The bassoonists "show virtually no bassoon vibrato up to the 1950s".

The Vienna Philharmonic website states that today, with the flute, "as in all wind and brass instruments in the Viennese classics, vibrato is used very sparingly."

Philips notes that by 1931 the Vienna Philharmonic strings were reported to use uniform bowing, which was still unusual in Britain. As for portamento – sliding audibly from one note to another, a prominent effect among pre-war string players – the VPO strings' sliding in the early 1930s "sounds more deliberately expressive, and less a matter of routine, than that of British orchestras. This is partly because of the firmer dynamic shaping of the melodic line, partly because of the warmer and fuller string tone." Further, he hears "strong evidence of a free approach to portamento" – that is, of "different players shifting at different points" within the same phrase (which, he shows, was standard internationally in pre-war orchestral playing). He notices a reduced use of portamento in recordings from 1931 to 1936, but in 1936 also notes that the VPO strings still make "conspicuous" use of portamento in Mozart, where British orchestras by this time were using less of it in Classical-era composers. Finally, he hears a "trend towards greater subtlety in the use of portamento" post-war, with "only discreet portamento" in a recording under Herbert von Karajan in 1949.

Controversies