The whimsically titled The Ascent of the Equestrian in a Balloon is a perfect window into the mind of composer Stephen Hartke, whose boundless imagination and creativity is represented by four works in this latest release from BMOP/sound. The inspiration for Ascent was a quirky, surreal 18th-century woodcut, and it’s a playful piece written in celebration of the composer’s two-year-old son’s birthday. Spanning a period of three decades, the other works on the disc cover a range of characters and influences. Alvorada, subtitled “three madrigals for string orchestra,” is a melodic, polyphonic exploration of medieval lyric poetry. A Brandenburg Autumn, written for the Orpheus Chamber Orchestra’s “New Brandenburgs” commissioning project, is a dialogue, from a modern perspective, with Bach’s groundbreaking orchestral works. Muse of the Missouri is rooted in a sense of place: the celebrated fountains of Kansas City, MO, where the composer has many friends and colleagues. The performers of the Boston Modern Orchestra Project, led by Gil Rose, shine in both small and large ensemble groupings.