fond of the boys' singing
'Absorbed in the boys' singing' — Kṛṣṇa loves the singing of the cowherd boys; in S.B.G 10.11.39 he is described listening to their forest songs with rapt attention as they go out daily.
बालकोद्गीतनिरतो बाहुक्षेपोदितप्रियः ।आत्मज्ञो मित्रवशगो गोपीगीतगुणोदयः॥
bālakodgītanirato bāhukṣepoditapriyaḥ ·ātmajño mitravaśago gopīgītaguṇodayaḥ
fond of the boys' singing
'Absorbed in the boys' singing' — Kṛṣṇa loves the singing of the cowherd boys; in S.B.G 10.11.39 he is described listening to their forest songs with rapt attention as they go out daily.
who showed his delight by waving his arms
'Dear to his friends through arm-throwing games' — Kṛṣṇa plays wrestling-style games where the boys throw each other's arms about; his playful equality with his friends is beloved.
the knower of the Self
'Knower of the Self' — Brahmā in his hundred-verse hymn acknowledges that Kṛṣṇa knows the ātman directly because he IS the ātman; he is the antaryāmī behind every consciousness.
who lets himself be won over by his friends
Kṛṣṇa goes wherever his friends wish to go; he plays the games they suggest; he is 'controlled by his friends (mitra)' in the Vṛndāvana woods, voluntarily subject to their desires out of pure love.
the rising of whose virtues the gopīs sang
In the Gopī-gīta (one of the Bhāgavata's most celebrated hymns), the disconsolate gopīs sing of Kṛṣṇa's qualities; the text presents this as the highest devotional poetry, revealing his guṇas through their longing.