U2 began its public performance life in small venues in Dublin in 1977, occasionally playing at other venues elsewhere in Ireland. In December 1979, they performed their first concerts outside Ireland, in London, and in 1980 began extensive touring across the British Isles, developing a following. Their debut album "Boy" was released in 1980. In 1981, leading up to the October Tour, Evans came very close to leaving U2 for religious reasons, but he decided to stay. During this period he became involved with a group called Shalom Tigers, in which bandmates Bono and Larry Mullen Jr. were also involved. Shortly after deciding to remain with the band, he wrote a piece of music that later became "Sunday Bloody Sunday". The Edge's style of playing guitar is distinguished by his chiming timbres, echoing notes, sparse voicings, and extensive use of effects units. He favours the perfect fifth interval and often plays chords consisting of just two notes, the fifth and the root note, while eliminating the third. This style is not explicitly in a minor or major key, but implies both, creating a musical ambiguity. For these chords, he often plays the same notes on multiple strings, some which are left open, creating an Irish-influenced drone. Against this drone, he changes other notes to imply a harmony. Among the Edge's signature techniques are playing arpeggios, sixteenth note percussive strumming, and harmonics, the latter of which he described as "so pure and finely-focused that [they have] the incredible ability to pierce through [their] environment of sound, just like lightning". The Edge takes a relatively understated approach to guitar playing, viewing notes as "expensive" and preferring to play simple parts that best serve their song. He eschews virtuosity in favour of "atmospherics, subtlety, minimalism, and clever signal processing", according to "Guitar Player". Rather than emulate common playing styles, the Edge is interested in "tearing up the rule book" and finding new ways to approach the instrument. He cited guitarists such as Tom Verlaine of Television, Rory Gallagher, and Patti Smith as some of his strongest influences. The Edge's guitar sound is frequently modulated with a delay effect set to a dotted eighth note for rhythmic effect. After acquiring his first delay pedal, the Electro-Harmonix Memory Man, he became fascinated with how to use its return echo to "fill in notes that [he's] not playing, like two guitar players rather than one".