So far Strzelecki has written 117 compositions which in their absolute majority consist of many movements (290 pieces in total, 25 hours ca. in leghth) or different and contrasted sections. He has focused on every genres, so that his output divides in two main fields of composing activity - instrumental music (orchestral, chamber, piano solo) as well as vocal-instrumental (cycles of songs or separate compositions). All is complemented by electronic pieces.
In emotional dimension, Strzelecki’s music is often very expressive and intensive (even - let us say - romantic).
In the matter of formal construction he has used traditional settings (sonata form, rondo, variations, passacaglia) and one-movement segmental organized schemes. In first case stable elements as themes, motives, harmonic units are the subject of developing (transforming) procedures, e.g. 12 symphonies (2017-2024), 3 symphonic poemes (2001-2011), in 3 solo concertos with orchestra (organ, piano, flute, 2002-2024), in 18 string quartets (2001-2024), in the cycle of 16 sonatas for different solo instruments with piano (violin, oboe, English horn, bassoon, French horn, cello, trumpet, trombone, tuba as well as piano and harp solo), chamber compositions as Piano Trio (1998), Piano Quartet (2021), Piano Quintet (2003), String Trio (2021) and numerous songs for voice and piano (set in cycles or separate) as well as sacred works, e.g. Mass for soloists, choir, organ and orchestra (2002, rev. 2021).
One-movement segmental settings are built more freely, with sections contrasted in material, texture and mood (some of them are lyrical and the others are vital). The episodes are planned in rondo-like form with allusions to the arch (reprise - mirror or retrogradal) patterns. This kind of musical 'story-tale' presents Ballade-Lullaby for piano (2009).
After 2000 he adopted more decisively repetitive technique. This procedure indicates in his usage of phase shifting patterns succeeding with meter-changing effects. Material is frequently organized with polyphonic procedures as canon, fugue producing more mobile textures – Organ Concerto (2002), String Quartet No. 2 (2012), Piano Concerto (2012).
Experiences with electronic output in pieces like Episodes for Tape (2001), In the Beginning was Chaos for tape (2009) and Smolensk 2010 for tape (2010) directed him on researching more complicated textural shapes. He has used the simultaneous layers technique – Mood Swings for Organ and Brass Quintet (2008), Summer Dreams for 14 Players and Tape (2008), Textures for 2 Pianists and 2 Percussionists (2009). This method is clearly evident in multilevelled opposite sections of Summer Dreams, where jazzy-rhythm main theme is superimposed on contrasting material of strings and other instruments.
His musical language evolved from chromatic-centralized – Piano Trio (1998) and free dodecaphonic - Episodes for Tape (2001) to more diatonic (modal) and euphonic – Piano Concerto (2012). Recently, however, Strzelecki employs again dodecaphony (strict in the 13th String Quartet "Dodecaphonic" [2022], and higly chromatic structures beside of modal ones - 9th Symphony "Victory" for Orchestra [2021]).Harmony is important factor in all his compositions where tritone-forth vertical structures are changing with Ravelian multi-thirdal polychords based on diatonic scale's full spectrums.
Strzelecki didn't resign from melodic element, which is evident in all his pieces. Driven by his passion to history and diverse traditions he uses too quotations which symbolic dimension strengthen message of asemantical art of sounds, for example "Sub Tuum Praesidium" (in Sonata for Violin and Piano [2000]), "Nearer my God to Thee" (Piano Quintet [2003]) and "Bogurodzica" (Voices from Old Poland for Orchestra [2011]). His interest in history is evident as well in program works, e.g. "Katyn Elegy. In Memory of the 17th September 1939" for Wind Orchestra (2010, rev. 2020), Symphony No. 2 "The 4 Places in Time & Space" for Orchestra (2018) - 2nd movement is dedicated to the Warsaw Uprising 1944, Symphony No. 5 "Surprise" for Orchestra (2020) - the 4th movement (Finale) describes "19.09.1939. Wólka Węglowa. The Last Mounted Charge". The inspiration is often draw from actual events, for example in Smolensk 2010 for Tape (2010), Symphony No. 10 "Between Dance and War" for Orchestra (2022).
Important field of his output build songs with piano or chamber accompaniment. It is manifesting e.g. in independant vocal-instrumental compositions - Interrogation of Angel for Baritone and Piano to the Lyrics by Zbigniew Herbert (2008), as well as in cycles: Five Songs to the Lyrics by Kazimiera Iłłakowiczówna for Mezzosoprano and 4 Instruments (1998), Nine Songs for Tenor and Piano to the Lyrics by Jan Kochanowski (2009), Three Spanish Songs to the lyrics by Gustavo Adolfo Becquer for Soprano and Piano (2013).
Polishness or universal dimension of Strzelecki's music exists in folk elements. They are evident in different pieces in rhythms or Polonaise, Scottish reel's, Spanish dances or Siciliana figures. Mazurka irregular accentuated scheme fulfilled second Theme of rondo-sonata form in Piano Trio's (1998). Important element in his music is blues, evident just in slow movement (Lullaby) of the Organ Concerto (2002), and later e.g. in the Symphony No. 8 "American" (2021) and in the 14th String Quartet "Bluesy" (2022).
In the field of theory of music Strzelecki is concentrated on integral history of this art in practical (language, harmony, counterpoint, composing and instrumental techniques as well as more abstract (aesthetical, etc.) levels.