The Middle: Bridge Track Finder
Sequencing music on radio means thinking in transitions. A jarring jump in energy or mood between songs breaks the listener's experience. DJing is picking the right songs to construct a musical journey. I built The Middle to help me find the song that belongs between two others.
The core design problem: A “similar” song isn't the same as a “bridge” song. Recommendation engines find songs that sound alike. A bridge track needs to make the A→C journey feel intentional, thinking directionally, not by averaging.
I encoded that reasoning into a scoring system across four dimensions: Energy (still to sparkling), Mood (dour to elated), Tempo (slow to fast), and Genre Shift (close to wild). Each dimension has tonal anchors I wrote into the prompt — Nine Inch Nails anchors the dour end of Mood; Katrina and the Waves anchors elated, and other songs defined the space between. That specificity gives Claude a shared frame of reference rather than abstract instruction.
The architecture splits the work between what each service does best. Last.fm's similarity graph seeds 50 candidates. Claude then acts as an evaluator (rather than a generator), validating each track against its own knowledge, discarding anything it can't describe with confidence (a hallucination check I added after early testing), and scores the rest. It returns ranked JSON: up to five suggestions with dimension scores, texture tags, and a sentence explaining the bridge logic.
The Genre Shift dimension is where my own taste as a radio host lives. I program an eclectic show — I want the wild end of the scale, mixing genres instead of staying on the path of “similar.” I baked that preference into the prompt, meaning the tool is tuned to my aesthetic, not a generic one.