20th century, the pedal division also underwent changes. The pedal divisions of the Baroque era often included a small number of higher-pitched stops, which allowed performers to perform higher melodies on the pedalboard. In the 19th century and early 20th century, organ designers omitted most of these higher-pitched stops, and used pedal divisions which were dominated by 8′ and 16′ stops. This design change, which coincided with the musical trend for music with a deep, rich bass part, meant that players used the pedalboard mainly for bass parts. By the mid-19th century, the pedal part of organ music was increasingly given its own staff, which meant that composers and transcribers began writing organ music in three-stave systems (right hand, left hand, and pedal keyboard). Whereas early organ composers left the way that pedal keyboard lines were played to the player's discretion, in the later 19th century, composers began to indicate specific foot actions. In addition to telling the organist whether to use the left or right foot, symbols indicate whether they should use the toe or heel. A "^" symbol indicates the toe, and a "u" or "o" indicates the heel. Symbols below notes indicate the left foot, and above notes indicates the right foot. Swedish organist L. Nilson published a method for the pedal keyboard, the English translation of which was titled A System of Technical Studies in Pedal Playing for the Organ (Schirmer, 1904). Nilson lamented that it "...is a melancholy fact that only very few eminent organists since Bach's time have made it their business to lift pedal-playing out of its primitive confusion..." (page 1 of Preface). He argued that the great organ pedagogues such as Kittel and Abbe Vogler did not make any efforts to improve the "...system of playing on the pedals". Nilson makes one exception from this critique: the organ method of J. Lemmens, who he praises as having reformed pedal playing by introducing "...sound principles of execution" (page 2 of Preface). Nilson's pedal method includes scale and arpeggio studies, polyphonic studies with both feet playing in contrary motion, studies written in parallel octaves, and studies written in thirds. 1990s–2000s In the 1990s, standalone electronic MIDI controller pedalboards became widely available on the market. MIDI pedalboards do not produce any tones by themselves, and so they must be connected to a MIDI-compatible electronic keyboard or MIDI sound module and an amplified loudspeaker to produce